CA1145027A - Exploration system for enhancing the likelihood of the discovery of deposits of ore, marker rock and/or economic minerals - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
EXPLORATION SYSTEM FOR ENHANCING THE
LIKELIHOOD OF THE DISCOVERY OF DEPOSITS
OF ORE, MARKER ROCK AND/OR ECONOMIC MINERALS

The present invention provides for the accurate mapping of shallow crustal earth formations by means for refractive seismic waves to identify structure as well as elastic parameters of the strata undergoing survey to indicate deposits of ore, marker rock, economic minerals and the like. In one aspect of the present invention, a "roll-along" technique is used in the field, such technique being both practical and economical. In accordance with another aspect of the invention, there is a provision for (i) accurate separation and determination of seismic shear and compressional responses using two-dimensional hodographs; (ii) stacking displays that allow for accurate identification of shape of the surveyed strata; and (ii) final depth displays of the refracting bed segments associated with seismic shear and compressional wave velocities a well as Poisson's ratio to indicate presence of ore, marker rocks, economic minerals and the like.

Description

OO1 RCOPr o- rnE l~V~NTIO~
002 The present invention relates to the exploration for 003 deposits of ore, marker rock and economic minerals in the shallow 004 crust of the earth using seismic exploration techniques, and more 005 particularly to mapping the shallow crustal earth formation by 006 means of refractive seismic waves separated by a computer-domi-007 nated 2-D hodograph process into shear and compressional 008 responsesl to identify structure as well as elastic parameters of 009 the strata undergoing survey.
010 In this application several terms are used and are 011 defined as follows: the term l'hodograph" means a plot of particle 012 motion in two-dimensional polar coordinate units as a function of 013 time; the term llmarker rock" means rock that identifies ores, eco-014 nomic minerals, metallic and non-metallic minerals and/or minerals 015 or rocks capable of supporting and/or at one time containing steam 016 or water at elevated temperatures. The term "ores'l means rocks 017 and minerals that can be recovered at a profit J and includes not 018 only metals and metal-bearing minerals, but also a plurality of 019 non-metallic minerals such as sulfur and fluorite. The definition 020 may also be rock containing small amounts of useful minerals or 021 may be rocks in a massive ore-bearing strata. The term "economic 022 minerals" includes concentrations sufficient to allow economic 023 recovery and/or are in a form that permits economic recovery such 024 as building stones, industrial materials (abrasives, clays, refrac-025 tories, light-weight aggregates, and salt), and includes the term 026 "ore minerals" (compounds valued for their metal content only) 027 within its definition.

029 Accelerating growth of the world's population, combined 030 with improved standards of living throughout the world, have 031 greatly increased demand for all types of mineral products. At 032 the same time, there have been attempts to shift to alternate 033 - 2 - ~

001 sources of energy such as to use steam or water at elevated tem-002 peratures in situ for driving compressors and the like. Such geo-003 thermal reservoirs are likewise being sought for the same reasons 004 described above and are usually in association with deposits which 005 can be designated as "marker rocks". Unfortunately the contrast 006 between physical properties of economic ore minerals and country 007 or host rock surrounding them are not well defined by conventional 008 surface exploration techniques. In zones of interest, whether an 009 anomaly of interest is from a valuable ore, mineral, etc., or from 010 some other associated rock material having no economic importance, 011 is a most difficult question to answer. This is primarily due to 012 the fact that ore, economic mineral and marker rock deposition are 013 under cover and cannot be observed at the earth's surface.
014 In oil and gas exploration, seismic refraction shooting 015 has been well known and practiced for decades. But because reso-016 lution of events is limited in the vertical direction to shallow 017 structures, crews performing refraction shooting have not used 018 arrays having severity overlapping inline positions. Additionally 019 applicability in the exploration sense of such a refraction 020 technique, say, for discovery of new deposits of ore, marker rock 021~ and economic minerals, did not exist. Heretofore, in such refrac-022 tion shooting, as reported in the book, 'IIntroduction To Geo-023 physical Prospecting", M. B. Dobrin, 2nd Ed., McGraw-Hill, 1960, 024 the detector positions are usually designated Xl, X2 Xnl with 025 the shot point and detector positions being positioned to provide 026 end-shooting sequences only. Successive shots at uniform or 027 almost uniform intervals, adjacent to the ends of detector 028 spreads, say, adjacent to the near detector position Xl and the 029 far detector position Xnl provide source waves. Then the detector 030 spread is advanced; its new end position Xl' becomes superimposed 031 on the Xn position of the prior spread. In that way, provision 032 can be made for a "tie point" from refraction record to refraction record but not for systematically associating at least two traces with each inline position along the line of survey.
SUMMARY OF THE INVENTION
In accordance with one aspect of this invention 5 there is provided method of accurately determining shape and elastic parameters of an earth formation to identify ore, marker rocks, economic minerals or the like, using a refrac-tion exploration field system including a series of detec-tors, positioned along a line or survey at inline positions 10 Xl~ X2~ . Xn and at least one seismic source located adjacent to said detectors for producing a seismic wave for travel through said formation: (a) generating a seismic wave at a first sourcepoint location adjacent said series of detectors; (b) after said wave undergoes refract~on, detect-15 ing arrival of a refracted wave at said series of detectorsat said inline offset positions, to obtain a first set of traces associated with said offset positions Xl, X2, ... Xn;
(c) repeating steps (a) and (b) by generating a second wave at a second sourcepoint adjacent to inline position Xn of 20 said detector positions, and detecting said refracted wave to obtain a second set of traces;. td) advancing said series of detectors a selected number of inline posi~ions or fractions thereof and repeating steps (a), (b) and (c) above to obtain additional sets of traces, but in which said additional sets 25 of traces are associated with more than two inline positions overlapping common inline positions of said first and second sets of traces; (e) dist.inguishing arrival times of shear waves from compressional waves by means of two-dimensional hodographs generated by a computer-dominated process; and (f) analyzing arrival times of at least one segment of (.i) shear waves and (ii) compressional waves as a function of in-line position whereby shape of said earth formation as well as elastic parameters indicative of likelihood of said formation being an ore, marker rock, economic mineral, and ~he like~ are provided.
In accordance with another aspect of this invention there is provided in accurately determining shape and elastic parameters of an earth formation to identify ore, n~rker rocks, economic minerals or the like, using a refraction exploration field system including a series of detectors, positioned along a line of survey at inline positions Xl, X2, ... Xn and at least one seismic source located adjacent to said detectors for producing a seismic wave for travel through said formation, means for distinguishing arrival times of refracted shear waves from compressional waves by means of two-dimensional, generated hodographs, and means for plotting a series of said distinguished refracted travel time values ve~sus horizontal offset coordinate annotated by sourcepoint-profile number and refraction arrival direction indicated by sourcepoint offset positions at one of a forward and trailing inline position X
and Xn of said detectors, slope of said travel time values versus offset being indicative of apparent P-wave and/or S-wave velocities, said sourcepoint offset positions being align~
able along an imaginary line of ascertainable slope.
The present invention has been surprisingly success-ful in indicating deposits of ore, economic minera]sand marker rock in the earth's crust. A key to interpretation: extremely accurate resolution of refraction compression versus shear wave responses using a computer dominated 2 D hodograph process.
Such resolution uses techniques that are both practical and economic, to aliow accurate identification of the shape o surveyed strata as well as to allow extremely accurate assess-ment of their seismic shear and compressional wave velocities as a function of depth.
~4a-In accordance with the present invention, resolution of refractor shape uses data provided by a field system that utilizes a "roll-along" technique of shifting source and detector arrays along a line or lines parallel with the line of 5 survey whereby the resulting refracted seismic data can be systematically indexed to offset position. Preferred construc-tion of the sources and detectors: each source is preferably a line source of dynamite, while the detectors are preferably 3 component detectors which provide outputs proportional to 10 deviations in vertical and horizontal directions at the earth's surface, although single direction (vertical) detectors can also be used, in accordance with collection aspects of the present invention. During collection, an array of sources and detectors is advanced in selected increments along the line of 15 survey, with the resulting refraction data processable to discern compressional from shear wave responses, to provide overlapping stackable displays indexed to common inline position and to refraction travel direction.
Data patterns can be classified so that: (1) 20 velocities of the shear and compressional waves can be accurately indicated via 2-D hodographs; and (2) there is an indication of the shape of the strata under survey based on posted P-wave or S-wave breaktimes.

-~b-001 Ultimately, a inal depth display of the refractor bed 002 segments annotated with shear and compressional wave velocities as 003 well as Poisson's ratio can be provided, such display being highly 004 indicative of deposits of ore, marker rock and/or economic 005 minerals in the refractor beds, especially if vertical dikes are 006 shown.
007 SPECIFIC DESCRIPTION OF TH~ DRAWINGS
008 FIG. 1 is a schematic section of an earth formation illus-009 trating the mechanism of transmission of refracted seismic waves;
010 FIGS. 2 and 3 are time-distance and ray path plots re-011 spectively for the earth formation of FIG. l;
012 FIGS. 4A, 4B and 4C are schematic diagrams of wave propa-013 gation within solids to illustrate compressional waves, shear 014 waves and Rayleigh waves, respectively.
015 FIG. 5 is a schematic diagram of an array of sources and 016 detectors positionally arranged along a line of survey in which 017 the sources and detectors are incrementally moved along the lines 018 of survey to provide higher resolution of refracting interfaces, 019 such advancement being analogous to a "roll-along" technique 020 conventional in reflection seismology;
021 FIG. 6 is a perspective view of a seismic source used in 022 the array of FIG. 5;
023 FIG. 7 is a refraction record shot in opposite 024 directions using the array of FIG. 5;
025 FIG. 8 is a schematic diagram of equipment useful in 026 carrying out the present invention;
027 FIGS. 9 and 12 are plots of data provided in the array 028 of FIG. 5 transformed in accordance with the teachings of the 029 present invention;
030 FIGS. 10 and 11 are details of the plot of FIG. 9;
031 FIG. 13 is a depth plot constructed rom the plot of 032 FIG. 12;

001 FIGS. 14 and 15 are typical final displays in accordance 002 with the teachings of the present invention;
003 FI~S. 16, 17, 18 and 19 relate to modified forms of the 004 present invention;
005 FIG. 20 is a partially schematic diagram of a 3-compon-006 ent detector useful in the array of FIG. 5 for distinguishing com-007 pressional and shear wave responses at the detector stations DSl, 008 DS2 etc., in accordance with a modified aspect of the present 009 invention;
010 FIGS. 21 and 22 are flow charts of a computer-dominated 011 process for distinguishing the compressional and shear wave 012 responses of the detector of FIG. 20;
013 FIG. 23 is a typical plot provided by the modified 014 method of FIGS. 21 and 22.
015 DESCRIPTION OF THE PREFERRED EMB_DIMENT OF THE INVENTION
016 In order to understand certain aspects of the invention 017 a brief review of the history of refraction seismology is in order 018 and is presented below.
019 FIG. 1 illustrates the mechanism for transmission of 020 refracting waves in an earth formation 9.
021 In FIG. 1 the formation 9 consists of a two-bed model, 022 i.e., beds 10 and 11, each with homogeneous and isotropic elastic 023 properties. Upper bed 10 lS separated ~rom the lower bed 11 by 024 horizontal interface 12. The upper bed 10 has a velocity less 025 than that of lower bed 11, i.e., the beds increase in velocity as 026 a function of depth. The surface 13 of the formation 9 is sepa-027 rated from inter~ace 12 by a depth z. Compressional velocity of 028 the seismic wave in the upper bed 10 is assumed to be Vo while the 029 compressional velocity in the lower bed 11 is Vl. If a seismic 030 wave is generated at point S, the energy travels with hemi-031 spherical wavefronts through bed 10. Detector 14 is placed 032 atpoint D, at the earth's surface 13, a distance X from S; the 001 wave traveling horizontally through upper bed 10 reaches the 002 detector 14 before any other wave (if X is small). For large 003 values of X, the wave traveling along the top of the lower bed 11 004 (having a higher speed Vl) overtakes the direct wave, however.
005 The mechanism by which energy is transmitted from S to D along the 006 indirect paths SA, ~B, and BD has been analyzed mathematically.
007 Briefly, when the spherical wavefronts from S strike the interface 008 12 the velocity changes and energy is refracted into the lower bed 009 11 according to Snell's law. At some point A on the wavefront, 010 the tangent is a sphere in the lower bed 11 and is perpendicular 011 to the boundary interface 12. The ray corresponding to this 012 wavefront now begins to travel along the interface 12 with the 013 speed Vl of the lower bed 11. By definition, the ray SA strikes 014 the interface 12 at the critical angle. In Figure 1, the wave-015 fronts below the interface 12 travel faster than those above. The 016 interface 12 is subjected to oscillating stresses. As a conse-017 quence, continuous new disturbances are generated along interface 018 12 spreading out in the upper bed 10 with a speed Vo. The 019 spherical waves adjacent to point B in the lower bed 11 travel a 020 distance BC during the time the wave in the upper bed 10 attains a 021 radius of BE. The resultant wave front above the interface 12 022 follows the line CE, making an angle ic with the boundary inter-023 face 12 in acccordance with the following equations:
024 BE Vot Vo sln ic = BC ylt Vl 028 The angle (ic) which the wavefront makes with the horizontal is 029 the same as the ray makes with the vertical so that the wavefront 030 will return to the surface at the critcal angle (Sin~l Vo/Vl) with 031 respect to the vertical.
032 FIGS. 2 and 3 illustrate time-distance and ray path 033 plots of data associated with the earth formation 9 of FIG. 1.

001 In FIG. 3, the wave is seen to travel along paths 002 AB-BC-CD2 and AB-BC-C'D3. In FIG. 2, a distance called the "criti-003 cal distance xc'' is shown, and is defined as the distance measured 004 from the shot point to intersection 15 of linear segments 16 and 005 17. Note with respect to FIGS. 2 and 3 that a direct wave can 006 travel from point A to a detector at a speed V~, so that T = X/Vo.
007 This is represented on the plot of the T-vs.-X in FIG. 2 as 008 straight line segment 16 which passes through the origin and has a 009 slope of l/Vo. At distances less than the critical distance Xc~
010 the direct wave reaches the detector first. At greater distances, 011 the wave refracted by the interface arrives before the direct wave 012 since it has been previously shown that the wave that travels 013 fastest from point A to points D2 or D3 approaches the interface 014 12 at the critical angle and propagates horizontally along the 015 interface 12 with the speed Vl of lower bed 11 and returns to the 016 surface 13 at the critical angle, i.e., along paths ABCD2 and 017 ABC'D3 of FIG. 3.
018 From FIGS. 2 and 3, the following equations can be 019 derived:
020 (1) sin ic = V0/Tl;
021 (2) T - X/Vl ~ 2Z/V12 - Vo2/ VlVo; and 022 (3) Ti = 2Z/V12 - Vo2/VlVo, where 023 ~ is the total time along the ray path of interest and 024 Ti is the intercept time of the time-distance plot.
025 While FIGS. 1-3 deal with compressive seismic wave propa-026 gation within the earth, similar plots explain the travel of trans-027 verse or shear waves within the earth. In order to understand the 028 differences as well as similarities of these types of waves, refer~
029 ence should now be made to FIGS. 4A, 4B and 4C. Before such dis-030 cussion a brief explanation of elastic waves is in order and is 031 presented below.
032 Briefly, the simplest type of elastic wave propagation 033 in a homogeneous, isotropic infinite elastic medium consists of 034 _ ~ _ 001 alternating condensations and rarefactions in which adjacent 002 particles of solid are moved closer together and then farther 003 apart. If a pressure is suddenly applied to a medium at a point 004 source, the region within the material of the medium that is most 005 compressed will move outwardly from the disturbance, the distur-006 bance having a radius increasing at a rate determined by the elas-007 tic properties of the medium.
008 In FIG. 4A the wave has a direction of particle motion 009 that is the same (or at an angle of 180~ as the direction of wave 010 propagation. Such waves are referred to as compressional or P-011 waves. The speed of the compressional waves is related to the 012 elastic constants and density of the medium in a well-known manner.
013 In FIG. 4B, the particle motion within the transmitting 014 medium is at right angles to the direction of the wave propa-OlS gation. Since the deformation is essentially a shearing motion, 016 such waves are often referred to as "shear wavesn. The velocity 017 of any transverse waves also depends on the elastic constants and 018 the density of the medium.
019 Rayleigh waves of FIG. 4C are waves travelling along a 020 free surface of any elastic solid. The particle motion (in a 021 vertical plane) is elliptical and retrograde with respect to the 022 direction of propagation. Amplitude decreases exponentially with 023 depth. The speed is slower than P-waves or S-waves, and can vary 024 when a low-speed surface layer overlays a much thicker material.
025 Having now established a firm theoretical foundation for 026 the invention, the latter will now be described below with ref-027 erence to FIG. 5.
028 In FIG. 5, an array 20 of detectors Dl, D2 .... is 029 aligned along a parallel line 21, designated "the line of survey"
030 of the array. Each detector can be provided with the ability to 031 discern shear waves, and compressional waves through the use of a 032 three-component system of response. ey the term "three-component"

033 ~ 9 _ 001 is meant that one or more o~ separate detectors is provided with 002 the capability of detecting ~ibrations in two directions in the 003 horizontal plane and in a single direction along the Yertical 004 axis. In that way, electrical signals associated with the llthree 005 components" can be transmitted via cable array 22 to recorder/-006 storage unit 26, as separate signals for ~u~ther processing as 007 discussed below.
008 Sources Sl, S2 .... etc. of seismic waves are placed as 009 sourcepoints SPl, SP2 ..... etc. adjacent to end detector positions 010 DSl, DS40 -- etc. Sequential shots can be taken at each end.
011 FIG. 6 illustrates a typical source. It consists of 012 dynamite cylinders 23. A group of cylinders of dynamite, say, 013 nine, may be formed into 3 separate longitudinally aligned seg-014 ments 24a, 24b and 24c such that the axis of symmetry of each is 015 substantially perpendicular to the earth's surface and parallel to 016 each other. Within each segment, contact between each group of 017 the three cylinders 23 is along substantially parallel lines.
018 Each group of three cylinders of each segment 24a-2Ac provides 019 three separate lines of contact in a "closest packing order"
020 arrangement; that is to say, each cylinder 23 is in-line contact 021 with the remaining members of each group along an exterior wall 022 thereof. The source is activated via a dynamite cap conventional 023 in the art.
024 Returning to FIG. 5, the detectors Dl, D2 .-. etc. are 025 positionable at a series of stations, such as detector stations 026 DSl, DS2 etc. When the sources are located at the source-027 points SPl and SP2, and when sources therein are energized in 028 sequence, the refraction data that are produced are capable of 029 being indexed to detector positions DPl, DP2. etc. at the 030 recorder/storage unit 26.
031 Since spacing between adjacent detector stations DSl, 032 DS2 etc. and source points SPl, SP2, SP3 etc. determines OQl the resolution pattern of the array, the closer the spacing, the002 better the dip resolution. And the longer the array, the greater 003 the depth resolution. Offset positions of detector and sources in 004 a typical field arrangement are as indicated in FIG. 5. Preferred 005 spread length: 3900 feet. In-line spacing of detectors: 100 006 feet. In-line spacing of the sources with respect to the detector 007 spread: 50 feet. Variations, of course, occur depending on the 008 many factors indicated above.
009 Recorder/storage unit 26 connects to the outputs of the 010 detectors through cable array 22 and other appropriate signal 011 processing circuits (not shown) which can include indexing and 012 recording address means. The latter annotates the positions -- in 013 the field -- of the seismic source producing the energy (viz., the 014 source at each sourcepoint SPl or SP2 etc., as well as the 015 detector stations receiving the refracted energy, viz. stations 016 DSl, DS2.~. etc. In operation, after activation of sources Sl and 017 S2 at sourcepoints SPl and SP2, data records are produced at the 018 detector stations DSl, DS2 etc. Thereafter, the array is 019 advanced in the direction of arrow 29; that is to say, the array 020 of FIG. 5 is "rolled forward" whereby station DSl is advanced to 021 station DSs with appropriate relocation of the remaining detectors 022 at original stations DS6, DS7 etc., occurring. After new 023 sources S3 and S4 at the sourcepoints SP3 and SP4 are energized, 024 and seismic energy is received at the detector stations DSs, DS6 025 etc., a new field data record is generated at recorder/storage 026 unit 26. It should be noted in FIG. 5 in this regard that the 027 detector stations, D5s, DS6 etc., define common offset posi-028 tions so that indexing of the refraction location data as a 029 function of offset position at the recorder/storage unit 26 is a 030 somewhat firm requirement. In this regard, efficiency of the 031 "roll-along" technique can be somewhat enhanced by using a roll~
032 along switch such as described in U.S. Patent 3,61~,000, issued 001 November 2, 1971, for "Roll-along Switch" and assigned to the 002 assignee of this application.
003 Data addressing is also a function of the nature of the-004 detector positioned at stations DSl, DS2, etc. Assume at each 005 detector station DSl, DS2 etc., e.g., the transverse component 006 output of each three-component detector is used, independently, to 007 measure shear wave response. Similarly, the vertical component 008 output of the same three component detector can be recorded, 009 directly, as the compressional wave response. Hence, processing 010 and addressing problems can be lessened.
011 As previously described, separate outputs of each 012 detector measure velocity of the displacement (movement) of the 013 earth's surface in three directions: (i) vertical displacement;
014 and (ii) two horizontal displacements at right angles to each 015 other. The former measures P-wave response; the latter relate to 016 S-wave response. Hence, three-component detectors are preferred 017 as array detectors under usual circumstances. However, it should 018 be noted that it is possible to use a single vertical component 019 detector under selected circumstances. Also a combination of both 020 types is possible, i.e., a 3-component detector can be used at the 021 stations DSl, DSs, etc. in conjunction with conventional vertical 022 detectors in betweent i.e., at stations DS2, DS3, DS4, DS6, etc.
023 Recorder/storage unit 26 can record and/or store the P-024 wave and S-wave data in separate data files in analog or digital 025 formats with such signals being convertible either at the field 026 site or at a remote location to conventional side-by-side wiggle 027 trace records. The data can also be annotated as to the direc-028 tions that the refractions were received, i.e., the data can be 029 associated with a source at a leading or at a trailing position 030 with respect to the detector spread.
031 FIG. 7, illustrates a typical record 27 of record/-032 storage unit 26.

S~27 001 As shown, timing marks are designated above the top of 002 the pair of records 27a and 27b, and indicate that the first wave 003 arrived about 1.75 seconds after the explosion of the source. The 004 first arrivals are indicated by a pronounced rise in amplitude 005 after which the traces remain disturbed, each arrival being charac~
006 terized by an upkick followed by a peak and a subsequent trough.
007 From the moveouts the apparent velocity can be calculated. In the 008 present invention, first-event refraction shooting is utilized, as 009 are second- and third-event refraction events.
010 In order to indicate intercept times -- and hence true 011 velocities -- the shape of the underlying strata including dip of 012 the bedding interfaces must be taken into account.
013 For example, consider that the refractions of a given 014 record have respective speeds of Vo and Vl and an interface dip-015 ping at a particular angle alpha between first and second beds, 016 see FIG. 1. If Zd is defined as the perpendicular distance from 017 shot to the interface at the up end of the line and Zu is the per-018 pendicular distance from shot at the downdip end of the line, then 019 the following formulas described the reraction travel times for 020 such a geometrv.
021 Td (total time shooting downdip) =
a~ 2zd c~ 0 y ~2~ 0 ~in~
024 Tu (total time shooting up-dip) =
0~5 2zu c03 l ~ 6 ~ ~ V 3ln~ a) 027 If the refracting interface is horizontal, however, the 028 actual depths are easily calculated as follows:

031 (Two layer case) Z ~depth) = ~ ~ L__ 034 (Three layer case) Zl 1 (~ 2 _ 2~ ~ )fiV~ -V

: .

5~æ~

001 But if there is dipping, further refinements must be 002 made, as suggested above, before the depths of the dipping beds 003 can be determined, as set forth in Dobrin, op. cit.

005 After collection, processing of the data is required.
006 Object of such processing: to associate a series of travel time 007 vs. offset plots of FI&S. 7A and 7B with selected detector spreads 008 of FIG. 5 to provide a guide to the shape of the strata under o09 survey.
010 While various types of equipment of both an analog and 011 digital nature can be used, the equipment of FIG. 8 has advantages 012 of simplicity and low cost, and so is presented in detail below.
013 Briefly, such processing utilizes either one of two data files:
014 (i) a P-wave data file associated with results of a vertical compo-015 nent of each three-component detector of the field array, or 016 (ii) an S-wave record associated with the horizon~al component of 017 the same detector of the same array.
018 In FIG. 8, separate magnetic recording and playback 019 systems are illustrated at 33 and 36. While the method of the 020 present invention could be performed with less apparatus than 021 shown herein by physically moving records back and forth between 022 recording systems, the process is more easily described and under-023 stood by referring to the two systems as shown. It should be 024 understood that other combinations of the apparatus, as well as 025 other types of recording, reproducing and data processing systems 026 are contemplated. An example of other such combinations would be 027 a properly programmed digltal computer.
028 The magnetic recording system 33 constitutes a drum 34 029 supported on a rotatable drive shaft 35 driven by a suitable 030 mechanism such as gear 37 through the worm shaft 38 and motor 3g.
031 Actual record processing in accordance with the present invention 032 will require careful speed control for rotation of the systems 33 001 and 36, as well as synchronization between the rotation o~ the 002 record drums and the movements of magnetic heads within each 003 system. The drum 33 is adapted with conventional apparatus, not 004 shown, ~or securing a record in the form of a magnetic tape 40 to 005 the periphery of the drum. Separate scanners 44 and 45 are car-006 ried adjacent to drum 34. The tape 40 includes two sets of data:
007 amplitude-vs.-time refraction data and a timing trace or marks 008 associated with activation of the source. The tape 40 is scanned 009 simultaneously ~y scanners 44 and 4S as a function of rotation of 010 drum 34. Movement of scanner 45 also occurs along the drum 33.
011 That is to say, after a single revolution of the drum 34, motor 41 012 is energized by apparatus to be described, to cause one step of 013 movement of the scanner 45 in the lateral direction. Scanner 44 014 is not activated by the motor 41, however; instead it remains 015 fixed at a known circumferential position relative to the drum 34.
016 It should be understood that different schemes may be 017 employed to provide individual control for the movement of each of 018 the heads. For example, the magnetic heads need not mounted on a 019 simple bar, but instead can be mounted as separate members that 020 are capable of individual circumferential movements around the 021 drum. The bar-type mechanism is illustrated here for didactic 022 clarity.
023 Scanner 45 is mounted on a threaded block 42 positioned 024 by rotation of worm 43. The threaded block 42 is guided by a 025 fixed rod 46 to prevent its rotation about worm 43. The worm 43 026 is driven from gear box 47 by a gear 48 and its engagement with 027 gear 49. Energization of motor 41 causes rotation of gears 48 and 028 49 and the consequent movement of the scanner 45 parallel to the 029 axis of drum 34. With each energization, the scanner 45 is moved 030 one trace transversely across the record to read the side-by-side 031 refraction traces.
032 Recording system 36 constitutes a drum 51 supported on a 033 rotatable shaft 52 driven by suitable mechanism such as gear 53, 034 - 15 ~

001 worm shaft 38 and motor 39. The drum 51 is adapted with appa-002 ratus, not shown, for securing the recording medium in the form of 003 magnetic tape 54 to the periphery of the drum 51. A single recor-004 ding head 55, connected through switchable contact 56, to be 005 described later, which cooperates with the tape 54 to produce a 006 recorded magnetic record. The single recording head 55 is mounted 007 on a threaded block 59 positioned by rotation of worm 60. The 008 threaded block is guided by fixed rod 61 to prevent its rotation.
009 Energization of motor 52 causes rotation of gear box 63 and the 010 consequent movement of the recording head 55 parallel to the axis 011 of drum 51.
012 The pitch of the worms 43 and 60 are so related that the 013 scanners 44 and 45 are moved step-by-step from one side to the 014 other of their respective drums while the cam 64 makes one com-015 plete revolution from one limiting position to another. Stepping 016 switches likewise can aid in providing appropriate synchronizatior;
017 of the system, as previously mentioned.
018 Energi~ation of the system illustrated in FIG. 8 is 019 provided from a power source 65 to motor 39 and through switch 020 contact 66 to the motors 41 and 62. Cam 69 on shaft 52 pushes on 021 rod 67, against the bias of spring 68 to close the switch 66, the 022 eccentric projection 6 9 of the cam 64 being the cause of contact 023 66 closing during the part of the revolution in which the magenti~
024 tapes on drums 34 and 51 are in such a position that their respec-025 tive heads 44 and 45 are in the peripheral gap between the begin-026 ning and the end of the tapes. During the relatively short time 027 that these heads are in that gap and, therefore, not transmitting 028 useful information, the heads are repositioned axially along thei~
029 respective drums while the drums 34 and 51 continue to revolve at 030 constant speed.
031 In operations refraction data on tape 40 of drum 34 032 flows via scanner 45 to a storage unit 70 and through an event 033 selector 71 to counter 72, and hence to tape 54 on drum 51.

001 ted analysis of the refraction data requires more than one trace 002 to identify events of interest. Hence, both storage 70 and event 003 selector 71 are interposed between scanner 45 and connector 56 as 004 shown.
005 Event selector 71 compares a group of three adjacent 006 refraction traces to detect arrival times within the central 007 trace, as set forth in U.S. Patent 3,149l302, Klein et al, for 008 "Information Selection Programmer Emphasizing Relative Amplitude, 009 Attribute Amplitude and Time Coherence," issued September 15, 010 1964, assigned to the assignee of the instant application. The 011 output of selector 71 is a single trace, modified in accordance 012 with selection code described in the above-identified patent.
013 Storage unit 70 can include a multi position relay 014 connected to a recording means, as described in U.S. Patent 015 3,149,303, Klein et al, for "Seismic Cross Section Plotter,"
016 issued September 15, 1964 and assigned to the instant assignee.
017 Counter 72 is selectively operated on a predetermined 018 "on-off" basis as follows: the activation spike of the source via 019 scanner 45 activates the counter 72 while the occurrence of a 020 refraction event on tape 40 of drum 33 terminates operations of 021 the counter 72, after which a reset signal resets the counter 72 022 to zero and simultaneously activates the marker of head 55.
023 Result: a refraction measure of time -- a "mark" -- is placed on 024 the tape 54 wound about drum 51. As the process is repeated, a 025 series of "timing marks" vs. ofset position is provided, in the 026 manner of FIG. 9. Operations cease through opening switch con-027 tacts 56 and 73 controlled by rod 74.
028 FIG. 9 illustrates a series of refraction travel time 029 vs. common offset plots 75 annotated by sourcepoint activation 030 number and/or position, provided by the apparatus of FIG. 8.
031 As shown, plots 75 are assembled in a paired, obliquely 032 segmented basis to better aid in stratigraphic interpretation. In 033 general, FIG. 9 shows individual plots of farward and reverse line 034 - ~7 -vs. offset signature diagrams displayed side-by-side using adjacent profile oblique segments 76 and 77, each containing a series of normalizing "~I" signature bars 78.
FIG. 9 is akin to the conventional common depth point stacking charts used in reflection seismology, and described in detail in U.S. Patent No. 4,316,268, issued February 16, 1982, for "Method for Interpretation of Seismic Records to Yield Indications of Gaseous ~ydrocarbons," W. S. Ostrander, and assigned to the assignee of the instant application.
In usual stacking diagrams as described in U.S. Patent No. 4,316,268, above, several separate variables are address-able including amplitude vs. time values, offset positions (say, detector, sourcepoint, centerpoint positions), source-point, profile line number, common offset lines, common centre-point lines, and common detector location lines, etc.
In the above-identified application, emphasis was placed upon centerpoint location in a two-dimensional coor-dinate system, say in a X-Y domain along oblique lines, with the third dimension being reserved for analysis and processing of the amplitude-vs.-time traces.
In FIG. 9, in the instant invention, centerpoint posi-tion in the offset direction and common centerpoint locations have been assigned to the third dimension, remaining co-ordin-ates of interest addressable in the X-Y domain.
Of particular importance: travel time vs. offset coordinate of refraction events annotated as to direction of refraction arrivals and their sourcepoints.
For example, along the top of FIG. 9, the detector stations are numbered in sequence, while along the bottom of FIG. 9, the sourcepoint locations are likewise indicated.
Each set of refraction-vs.-time values is plotted as shcwn with reference -~ to the-series of normalizing signature bars 78. Each bar 78 has a ~5~27 001 length equal to that of the detector spread plus twice the source-002 point offset distance with respect to ~he spread ends, as dis-003 cussed below.
004 In particular in FI~. 9, since plots 75 were generated 005 using an end-shooting array in which sources and detectors advance 006 4 detector intervals per shot point, the "H" bars 78 overlap.
007 Note further that each offset position (after initialization) is 008 associated with 8 separate time values so that such values can be 009 associated with common surface detector positions.
010 In order to geometrically associate generated data with 011 common surface position, or common offset position, address guid-012 ance, as provided by printed "H" bars 78, is of some importance.
013 Signature bars 78 form the ordinates of the display and 014 are seen to be paired into sets, each associated with an opposite 015 arrival direction of the refraction wave. Each pair is spaced a 016 constant distance, say, a value 2d feet where d is the rollalong 017 increment of the field procedure.
018 Vertical upright segments 79 of each bar 78 coincides 019 with the offset position of the sourcepoints, say SPl, SP3, 020 SPs .... alignable along oblique line 80, and SP12, SP14 .... etc.
021 alignable along oblique line 81.
022 Annotation of each H-bar 78 is preferably based on 023 sourcepoint position, and direction of ~ave travel. "Forward"
024 data profiles 76 designate that wave travel is in the same "~or-025 ward~ direction as array progression, while "reverse" data pro-026 files 77 refer to wave travel in the opposite direction as array 027 progression.
028 At the bottom of the display, the last-in-line profiles, 029 say the profiles Sz of profile segment 76 and profile column Sz+c 030 of segment 77, are related to the detector and shot point posi-031 tions in a manner convenient for easy display. Note that if 032 sourcepoint Sz is odd, then sourcepoint Sz+c is even, and vice 033 versa.

001 FIGS. 10, 11, 12 and 13 illustrate how the plots of FIG.
002 9 can be used to indicate shape and model depth of a formation 003 under survey.
004 In FIG. I0/ note that the travel time data are asso-005 ciated with certain particular H-signature bars of FIG. 9, viz., 006 bars 78a, 78b, 78c and 78d. I.e., the latter relate to and are 007 associated with the forward profile column 76 of FIG. 9, say, anno-008 tated to sourcepoints SPg, SPll, SP13 and SPls, as shown.
009 Values of travel time vs. offset are plotted as shown.
010 Note the intersection points of the plotted points occur 011 at breakpoints 82a, 82b, 82c and 82d. These breakpoints can be 012 connected by a line 83 having a slope about equal to that line sn 013 through the sourcepoints SPg, SPll, SPls etc., of the signa-014 ture bars 78a-78d. Result: the interpreter of the data can confi-015 dently assume that bedding to which the data relate is horizontal.
016 FIG. 11 illustrates travel times plotted for other cer-017 tain H-signature bars occurring later in time in the survey, say, 018 data associated with bars 78f, 78g, 78h, 78i and 78j, are also 019 related to forward column profile 76 of FIG. 9. These are anno-020 tated to, say, sourcepoints SP21, SP23~ SP25~ SP27 and SP29 a5 021 shown.
022 Note that here the breakpoints 85a, 85b, 85c, 85d and 023 85e do not align themselves parallel to line 80 through the source-02~ points SP21, SP23 etc. But instead these breakpoints aligned 025 themselves along a line 87 whose slope is the vertical. Result:
026 the interpreter can assume a vertical contact exists below the 027 near bed undergoing survey. Hence, appropriate formulas for the 028 geometry change can be implemented in ~he depth model as discussed 029 below.
030 FIGS. 12 and 13 illustrate a further example of the 031 method of the present invention in which the pairing of "H"
032 signature bars 78 of FIG. 9 has been changed to provide more 033 interpretive insight for th0 user.

001 As shown in FIG. 12, the adjacent pairing of H-bars has 002 been changed so that oblique column segments 91 and 92 no longer 003 are a combination of oddfeven or even/odd sourcepoints as before.
00~ Instead, the pairings are changed to emphasize a particular bed-005 ding structure of FIG. 13 below a certain sourcepoint location, 006 viz. sourcepoint 11 of FIG. 13.
007 In FIG. 12 note that the compressional travel time data 008 are associated with certain particular H-signature bars, viz. bars 009 90a, 90b, 90c, .... 90k, and bars 901, 90m .... 90v.
010 The former, in turnl relate to and are associated with 011 the forward profile segment 91, say, annotated to sourcepoints 012 SPl, SP2 SPll, as shown. The latter in turn relate to and ar~
013 associated with the rear profile segment 92 annotated to source-014 points SPll, SP12 -- SP21-015 Breakpoints are as indicated, with vertical lines 97a-016 97f being drawn through them for emphasis.
017 Note that since the lines 97a-97f are somewhat vertical 018 and deviate radially from common line~ through sourcepoints SPl, 019 SP2, SP3 .... etc., and through SP12, SP13 .... etc., the bedding o 020 interest is not horizontally disposed.
021 The compressional data of FIG. 12 further illustrate 022 that apparent refraction times have been greatly affected by the 023 shape of formation undergoing surveying, viz. by the presence of 024 dike 93 of FIG. 13 uplifted through deeper beds 94 and 95 but ter 025 minating well below upper bed 96.
026 Of course, it is apparent that the above H-bar data can 027 be easily used to indicate apparent compressional velocities as 028 set forth in FIG. 12. True velocity of the bed 96 can then be ca 029 culated using intercept time-distance relationships well under-030 stood in the art, see Dobrin, op. cit., assuming correct pairs of 031 forward and reverse plots, are utilized.
032 As to dike 93 of FIG. 13, the importance of using inter 033 cept times and apparent velocities associated with sourcepoint ~Si2~

001 "H"-bars which do not s~raddle breaklines 97a-97b and 97d-97e must 002 be emphasized. That is to say, intercept times and apparen~
003 velocities associated with "H"-bars 90k and 90v do not provide 004 correct results which can be directly associated with dike 93, 005 i.e., intercept times and apparent velocity deduced therefrom, 006 from which the velocity and depth can be calculated as shown in 007 FIG. 13, would be erroneous. Note that the slopes of the break-008 point lines are directly associated with the vertical slope of the 009 walls of the dike 93 of FIG. 13, however.
010 On the other hand, if the data of H-bars 90j and 90m are 011 used, the interpretive results would be correct.
012 Key to correctly interpreting H-bars 90a-9Ov: pick 013 H-bar data closest to breakpoints in the forward and reverse direc-014 ion but which do not straddle them, and so provide true indica-01S tions of the intercept time and apparent velocity of the dike 93 G16 of FIG. 13. Note also that the velocity magnitudes and intercept 017 times associated with chosen forward and reverse pairs of H-bars 018 also indicate the magnitude of the dips of the strata under sur-019 vey. From such data, the interpreter can be provided with informa 020 tion from which true velocity data can be determined; while the 021 intercept times and other distance-time data of FIG. 12 are used 022 to calculate true compressional velocity, similar plots and values 023 associated with shear waves are used, in a similar manner to calcu 024 late true shear velocity of each bed of interest with appropriate 025 final displays of such data being available, as required.
026 FIGS. 14 and 15 illustrate a field example of final dis-027 plays associated with various structures that have been surveyed 028 using the method of the present invention.
029 FIG. 14 is a plot of various elastic parameters at a 030 specific depth for a porphyry copper prospect, Stafford Mining 031 District, Arizona.
032 Curve 100 is a plot of compressional velocity at a 033 specific depth taken at various cross-sectional horizons; Curve 101 is a plot of shear velocity as a function of the same loca-tions; Curve 102 is a diagram of Poisson's ratio at the same depth; and Curve 103 is a plot of a bulk modulus-bulk density ratio at t~e same depth for the above-identified prospect.
Note at ~ault 104 and dike 105 the dramatic change in values of interest.
FIG. 15 is a depth-versus-horizontal survey position plot of the above Stafford District, Arizona, copper prospect.
Note that the depth values were calculated using the methods of FIGS. 12 and 13 in conjunction with appropriate geo-metrial formulas set forth in Dobrin, op. cit. Note further that over a given but changeable depth interval, interface bedding segments can be identified. The segments to the left of fault 104 are seen to exist at 106-119, and each can be addressed and stored for future reference, say, as to length, end-point locations, compressional and shear velocity values, Po~sson's ratio etc., as required. In that way, values stor-able in files within any analog or digital computer can be ordered out as required onto, say, a disk unit. Thereafter, any off-line digital plotter capable of generating the display of FIG. 15 is used in conjunction with the data on the disk unit. In this regard, equipment illustrated in "Continuous Automatic Migration," South African Patent No. 3623, John W.
Sherwood, assigned to the assignee of the instant application, is of interest, and can be used to address, index and store segments of data in accordance with the teachings of the pre-sent invention.
Such plotters are available in the art, and one pro-prietary model uses a computer-controlled C~T for optically merging onto photographic paper, as a display mechanism, the seismic data. Briefly, in such a plotter the data are con-verted to CRT deflection signals; the resultiny beam is dra~ on the face of the CRT and the optically merged record of the data is thereafter indi-. .~ .

001 cated, say, via photographic film. Then the film is processed in 002 a photography laboratory and hard copies returned to the inter-003 preters for their review. Additionally, the data could be plotted 004 by hand, if desired. But for usual applications, in which speed 005 is important, the plotter described above is preferred.
006 Modification 007 In some case, it may be desirable to use only single 008 component detectors in the field spread so that only vertical 009 displacement data is available. In such cases, modification of 010 processing equipment to provide separate P-wave and S-wave plots 011 prior to use of the apparatus of FIG. 8, is required. FIG. 16 012 provides such equipment.
013 With reference to FIG. 16, note that three separate mag-014 netic tape recording and playback systems are illustrated at 120, 015 130 and 160. While the method of the present invention could be 016 performed with less apparatus than shown herein by physically 017 moving records back and forth between recording systems, the 018 process is more ea$ily described and understood by re~erring to 019 the three systems as shown. It should be understood that other 020 combinations of the apparatus, as well as other types of record-021 ing, reproducing and data processing systems are contemplated. An 022 example of other such combinations would be a properly progr~mmed 023 digital computer.
024 Since the record contains both P-wave and S-wave energy, 025 velocity "filteriny" in accordance with this aspect of the present 026 invention can occur based on arrival time of the events of interes 027 The first magnetic recording system 120 constitutes a 028 drum 121 supported on a rotatable drive shaft 122 driven by a suit 029 able mechanism such as gear 123, worm shaft 141 and motor 142.
030 Actual record processing in accordance with the present invention 031 will require careful speed control for rotation of the systems 032 120, 130 and 160, as well as synchronization between the rotation 001 of the record drums and the movements of heads within each system.
002 The drum 121 is adapted with conventional apparatus, not shown, 003 for securing a refraction record in the form of a magnetic tape 004 124 to the periphery of the drumt such trace being one provided by 005 the refraction system of the present invention using single-006 component detectors for measuring vertical displacement only. A
007 plurality of magnetic heads, not individually illustrated, are 008 carried by a pivotally mounted head moving bar 125. The head 009 moving bar 125 is here illustrated with a pivot at its center so 010 as to be positioned in different transverse alignments with 011 respect to the periphery of the drum and the longitudinal axis of 012 the seismic record mounted thereon. The pivot is outside of the 013 drum so that the drum may be rotated with respect to the bar and 014 the headsO The individual heads are aligned with traces on the 015 record and reproduce the electrical signals represented on the 016 traces with differential time adjustments between traces caused by 017 the alignment of head moving bar 125 with respect to the record.
018 Since each trace is associated with a selec~ed detector field coor-019 dinate, the dimensional characteristics of the traces are ampli-020 tude-vs.-time-and-horizontal coordinate.
021 The pivotally mounted head moving bar 125 is moved about 022 its pivot by movement of a mechanical push rod 143 following a cam 023 144. The cam is rotated through gear box 145 from motor 146, and 024 the cam and gear reduction are appropriately designed to provide 025 for a total movement of head moving bar 12S between its pivotal 026 limits in a predetermined number of steps. After each single revo-027 lution of the drum 121, motor 146 is energized b~ apparatus to be 028 described, to cause one step of movement of the cam 14~. During 029 each stop of the bar 125 per single revolution of the drum 121, it 030 is evident that the group of traces thus generated can be identi-031 fied by a horizontal coordinate corresponding to the horizontal 032 position of the pivot point of FIG. 16.

001 It should be understood that different schemes may be 002 employed to provide individual control ~or the movement of each of 003 the reproducing heads and also that cams of a di~ferent contour 004 may be employed to produce stepped head movement in different 005 increments. For example, in apparatus actually used to carry out 006 the method of this invention, the magnetic pickup heads are not 007 mounted on a simple bar, but instead are mounted on separate 008 members that are capable of individual circumferential ~ovements 009 around the drum. The bar-type mechanism is illustrated here for 010 didactic clarity.
011 The signals from summing amplifier 97 are passed to 012 storage device 98 and thence to an event selector 99. Sophisti-013 cated analysis of traces to detect events requires more than one 014 trace in simultaneous processing. Hence, storage device 98 is 015 positioned between the amplifier 97 and selector 99 as depicted in 016 FIG. 16.
017 In U.S. Patent 3,149,302, Klein et al, for i'Informa-018 tional Selection Programmer Employing Relative Amplitude, Absolute 019 Amplitude and Time Coherence, n issued September 15, 1964, and 020 assigned to the assignee of the present application, a method and 021 apparatus for forming the comparative analysis of seismic traces 022 was disclosed. In that patent, a group of three adjacent traces Q23 are compared for selectional purpose to detect events within the 024 central one of the three traces. Since event selector 99 func-025 tions in accordance with predetermined selection codes (or sets of 026 rules) to identify certain amplitude excursions along each of the 027 sum traces from the storage device 98 that are believed to repre-028 sent coherent energy on the original record that, in turn, repre-029 sent probable refractions, the output from the selector 99 is a 030 single trace whose amplitude or intensity is modified according to 031 the picking selection code of the type described in U.S. Patent 032 3,149,302. That patent further discloses that the use of three 001 traces is arbitrary and the number of traces selected or the 002 comparison will be determined by the sensitivity p~ttern of the 003 array and by the time delay (moveout) employed in e~tracting the 004 directional information from the original field traces. However, 005 it should be noted that it is not necessary to produce and store 006 all of the directional traces before the selection process occurs, 007 since only a limited few are actually used at any one time in the 008 selection of eventsO Patent 3,149,303, Klein et al, for "Seismic 009 Cross Section Plotter," issued September 15, 1964, discloses a 010 temporary storage device useful in accomplishing the temporary 011 storage of directional seismic traces. As described in that 012 patent, a typical storage device includes a multiposition relay 013 connected to a multichannel recording means. As each sonogram 014 trace is produced from the original trace~, that trace is applied 015 through the multiposition relay to the recording means. Each 016 channel of the recording medium will have the necessary elements 017 to record, reproduce and erase the signals within itself.
018 Referring again to FIG. 16, if such a multiposition relay is used, 019 it can be stepped through each of its positions using, say, 020 linkage 143 connected as illustrated in FIG. 16 so that in each of 021 its successive positions the directional seismic trace produced 022 from a summing bar 125 will be applied to a different one of the 023 separate channels of the recording means.
024 Attention should also be directed to the fact that other 025 event selectors could be utilized in the present invention, as for 026 example that event selector described in U.S. Patent 3,273,114, 027 Stephenson et al, for "Ergodic Signal Picking, R issued September 028 13, 1966 and assigned to the assignee of the present application.
029 In that patent, there is described a method and apparatus for per-030 forming the selection of seismic events based on a statistical 031 deviation of instantaneous measured characteristics from measured 032 normalized average characteristics with respect to the original 001 record. However, if such a picking method were used, the appa-002 ratus of FIG. 16 would be somewhat modified. Likewise, combina-003 tions of the aforementioned devices and methods may also be useful 004 in carrying out the present invention. In this regard, since the 005 tailoring of steps to achieve specified selection goals may now be 006 of importance in the processing of seismic data, a method having 007 particular utility in the operating modes of the present invention 008 will now be described. It will become evident from the discussion 009 which follows that the method is, in essence, time-averaging event 010 detection and incorporates features of the event selectors and 011 methods referenced above. Briefly, in this method, for each sono-012 gram trace to be picked, a corresponding "control trace" is gene-013 rated, whose amplitude values as a function of time may be only 014 zero of unity. Multiplication of each sonogram trace by its corre-015 sponding control trace emphasizes those portions of the sonogram 016 trace considered to contain seismically meaningful events.
017 Now in more detail, the generation of the control trace 018 involves several steps, which may be thought of as being in two 019 separate, parallel groups of steps: (i) the first group of steps 020 consists of individually s~uaring and integrating each of the 021 traces of the original seismic record to produce a set of indi-022 vidual traces which represent the power in the original individual 023 traces. Then, the power traces are sonogrammed to produce a set 024 of "sonogram average power traces", one for each moveout used in 025 the sonogramming process; and (ii) the second group of steps con-926 sists of individually squaring and integrating each of the traces 027 of the original seismic record to produce a set of individual 028 traces which represent the power in the original individual 029 traces. Then the power traces are sonogrammed to produce a set of 030 "sonogram average power traces, n one for each moveout used in the 031 sonogramming process; and (ii) the second group of steps consists 032 of, first, individually squaring and integrating the regular sono-

2~

001 gram traces to obtain individual "power traces of a sonogram".
002 Then, the amplitude values on these traces are divided, point by 003 point, by the amplitude values on the previously derived, corre-004 sponding, sonogram average power traces. The result at this point 005 is a set of "normalized power traces", one trace for each trace of 006 the starting sonogram. The normalized ~races are ~hen scanned to 007 find portions whose values are above a threshold number, e.g., 008 0.20, and for each of the normalized traces a control trace is 009 then generated whose amplitude value is zero when that of the nor-010 malized power trace is greater than the threshold value and whose 011 amplitude value is unity when that of the normalized power traces 012 is greater than the threshold value. Finally, each of the start-013 ing sonogram traces is multiplied, point by point, by its corre-014 sponding control trace, to give a corresponding picked sonogram 015 trace, whose amplitude values are those of the starting sonogram 016 trace in the time intervals when the control trace was unity, and 017 whose amplitude values are zeroed out when the control trace was 018 zero.
019 The preceding steps to obtain picked sonogram traces by 020 control trace multiplication may be varied in many possible ways.
021 Variations include scanning the normalized power traces three at a 022 time, fitting parabolas to the coincident peaks, and comparing the 023 peak values of the fitted parabolas to the threshold value.
024 From event selector 99, the picked signals are passed 025 through switchable contacts 183, to be described hereinafter, to 026 recording system 130. System 130 constitutes a rotatable drum 131 027 mounted on shaft 132 driven by gear 133 through engagement with 028 worm 141 rotated by motor 142. The recording system 130 is pro-029 vided with a single recording head 134 to record the signals sup-030 plied from event selector 99. Recording head 134 is positioned 031 parallel to the axis of the drum in accordance with rotation of 032 worm 135 driven from drive motor 146 by mechanism similar to that 001 employed for pickup head 125 in system 120 so that head 134 is 002 moved step by step transversly across the surface of drum 131. In 003 each of its positions, recording head 13~ records on~o the magne-004 tic tape 136 of the recording system 130 a picked sonogram trace 005 derived from the record 124 of recording system 120.
006 The recording system 130 further includes a plurality of 007 pickup heads, not individually illustrated, carried on a pivotally 008 mounted head moving bar 137 illustrated with a pivot at its center 009 138. Head moving bar 137 is mounted and movable similarly to bar 010 125 of system 120. The individual pickup heads reproduce the elec-011 trical signals represented on the traces of the record recorded on 012 tape 136 and these signals are transmitted as individual signals 013 through conductors 139 to a trace selector 151 and then to a sum-014 ming amplifier 152~ Switchable contacts 184, to be described, are 015 provided between the recording system 130 and the trace selector 016 151.
017 The pivotally mounted head moving bar 137 is moved about 018 its pivot 138 by movement of a mechnical push rod 153 following a 019 cam 154. The cam is rotated through a gear box 155 from motor 156 020 and is appropriately designed to provide for a total movement of 021 the head moving bar 137 between its pivotal limits in a predeter-022 mined number of steps. After each single revolution of the drum 023 131, motor 156 is energized to cause one step of movement of the 024 cam 154.
025 When head moving bar 125 is aligned as illustrated in 026 FIG. 16, attention should be directed to the fact that the sensi-027 tivity of the collectively moving heads will be most represen-028 tative to signals having a moveout along the time axis of the 029 record proportional to angle alpha where alpha is the angle 030 between bar 125 and a horizontal line in the plane of tape 124.
031 If the length of the bar 125 intersecting imaginary verticals ema-032 nating from the surface of tape 124 passing through the left-most 001 and the most-right traces of the record 136 (or for that matter 002 any N traces), then the time moveout along the record, /t, is 003 equal to (Sin)L where L is the bar length. The resulting summed 004 signals from bar 125 aligned in the posi~ion depicted in FIG. 16, 005 thus can be said to represent the largest and most negative direc-006 tional trace of the process, and for reasons set forth in the 007 specification, supra, will be designated the (-60) millisecond 008 trace. The (-60) millisecond trace will be recorded as the left-009 most trace on record 136, as depicted in FIG. 16. Similarly, when 010 the moving bar 125 is positioned as illustrated in FIG. 16, the 011 heads will be most responsive to directional signals having a 012 record moveout which is the largest and most positive value of the 013 process. As the summed signals are recorded on record 136, such 014 summed signals will be recorded at the right-most trace, and for 015 reasons of clarification to be discussed below, it is designated 016 (+60) millisecond trace. Between the aforementioned left- and 017 right-most sonogram traces on record 136 there will be recorded 018 additional traces representing proportional moveout magnitudes 019 between the left-most and r ght-most traces with the zero moveout 020 trace usually being centered therebetween. The number of addi 021 tional traces can range between any convenient number, say, 10 to 022 30 traces, with about 20 being preferred.
023 By convention in the sonogram process, the summation 024 trace signals are recorded on record 136 at a longitudinal posi-025 tion along the trace corresponding to the time position of the 026 center or pivot point of summation angle or, in the case illus-027 trated, the center of bar 125. An event, appearing first in time 028 on the trace on the left of record 124 and later on the trace to 029 the right, would appear on a trace on record 136 to the left of 030 center with the event being recorded at a longitudinal position 031 along the record determined by the position of the pivot point of 032 the head moving bar 125 with respect to the longitudinal or time 033 axis of record 124.

001 Trace selector 151 is for the purpose of including, or 002 excluding, any individual sonogram trace from the sonogram record 003 136 so as to exclude or include only P-wave or only S-wave events 004 in the final record. That is, P-wave and S-wave events can be 005 easily separated with one or the other through selection codes 006 provided in trace selector 151. In this regard, attendant 007 circuitry within selector 151 is activated to cause inclusion of 008 representations of the sonogram trace, those representations 009 having either a positive or negative sign (with regard to the 010 latter distinction, amplitudes having negative signs bring about 011 amplitude inversion of the trace). Exclusion of representations 012 can also occur in which individual sonogram traces are prevented 013 from passage through the selector 151, and, accordingly, are 014 prevented from further processing in accordance with the 015 procedures of the present invention.
016 Trace selector 151 may be thought of as a set of trans-017 formers~ one for each trace to be fed into the selector 151.
018 Since it is usual to process traces in a selected group, selector 019 151 could consist of several separate transformers in parallel.
020 With the secondary of each transformer center-~apped to ground, 021 connection to one end of a secondary would give a voltage propor-022 tional to the input signal, and of the same sign, while connection 023 to the other end of the secondary would give a similar voltage, 024 but of the opposite sign. Non-connection to either end (switch 025 means inactivated), of course, would simply exclude the trace in 026 question. In actual practice, these conceptual transformers are 027 replaced by pairs of operational amplifiers capable of giving, for 028 each input channel, a pair of proportional outputs, one positive 029 and the other negative, and also capable, of course, of giving 030 zero output, when switched off.
031 Attention should now be directed to the fact that the 032 decision whether or not to include or exclude a particular sono-~5¢~

001 gram trace or group of traces at the selector 151 is not based or 002 criteria developed after the processing o~ the data has begun.
003 The criteria are developed and implemented by a seismologist prior 004 to the initial sonogramming step. Once a particular decision has 005 been made by the seismologist, the apparatus of FIG. 16 carries 006 out his commands using conventional circuitry such as a series of 007 switches whose actuation is scheduled prior to the initial proc-008 essing steps. For example, mechanical linkage 140 could be a 009 series of cams attached to a common shaft through gear box 155, 010 the cams coming into effect as a function of the angle of rotation 011 of that shaft. It should be pointed out, however, that linkage 012 140 is depicted as a mechanical unit for didactic simplicity only.
013 It indicates that the same mechanism which determines the settings 014 of head moving bar 137 should also determine the switch settings 015 of the switch means within selector 151. In practice, both the 016 head moving bar 137 and the switch means of trace selector 151 can 017 be actuated by stepping switches which step as a function of drum 018 rotation, to provide the required informational selection.
019 The traces passed through selector 151 are supplied to 020 summing amplifier 152 where they are combined to produce a single 021 output trace for each revolution of the drum 131. The summed 022 signal output from summing amplifier 152 constitutes individual 023 seismic trace-like signals and is passed to recording system 160.
024 Recording system 160 consitutes a drum 161 supported on 025 a rotatable shaft 16 2 driven by suitable mechanism such as gear 026 163, worm shaft 1~1 and motor 142. The drum 161 is adapted with 027 apparatus, not shown, for securing a recording medium in the form 028 of a magnetic tape 164 to the periphery of the drum. A single 029 recording head 165, connected to and through switchable contacts 030 185, to be described later, cooperates with the tape 164 to 031 produce a recorded magnetic record. The single recording head 165 032 is mounted on a threaded block 166 positioned by rotation of worm 033 ~ 33 -001 167. The threaded block is guided by fixed rod 16 8 to prevent its 002 rotation. Energization of motor 156 causes rotation of gear 159 003 and the consequent movement of the recording head 165 parallel to 004 the axis of the drum 161.
005 The pitch of the worms 135 and 167 and the contour of 005 the cams 144 and 154 are related so that the heads 125, 137 and 007 165 are moved step by step from one side to the other of their 008 respective drums while the cams make one complete revolution to 009 move the head moving bars 125 and 137 from one limiting position 010 to another. Stepping switches likewise can aid in providing appro-011 priate synchronization of the system, as previously mentioned.
012 Energization of the system illustrated in FIG. 16 is 013 provided from a power source 171 (through switch contacts 172 to 014 motors 146 and 156 ) and directly to motor 142. Cam 173 on shaft 015 16 2 pushes on rod 174, against the bias of spring 175, to close 016 the contacts 172. The eccentric projection 176 of the cam 173 017 causes contacts 172 to be closed only during the part of the revo-018 lution in which the magnetic tapes on drums 121, 131 and 161 are 019 in such a position that their respective heads 134 and 165 are in 020 the peripheral gap between the beginning and the end of the tapes.
021 During the relatively short time that these heads are in that gap 022 and, therefore, not transmitting useful information, the heads are 023 repositioned axially along their respective drums while the drums 024 121, 131 and 161 continue to revolve at constant speed~
025 Individual switching contacts are shown at 182, 183, 184 026 and 185, between bar 125 and summing amplifier 97, between event 027 selector 99 and recording head 134, and between cable 139 and 028 trace selector 151, and between summing amplifier lS 2 and head 029 165. The switchable contacts 182, 183, 184 and 185 are collective-030 ly operated by a linkage 186 and a master control rod 187. It 031 should be apparent that when contacts 182 and 183 are open, con-032 tacts 184 and 185 are closed, and that when contacts 182 and 183 033 - 3~ -001 are open, the contacts 184 and 185 are closed. In the ~down"
002 position, the first sonogramming process will be performed and in 003 the "up" position the second sonogramming will be performed.
004 The operation of the mechanism in performing the method 005 of the present invention should be readily apparent from the fore-006 going description of the apparatus schematically illustrated in 007 FIG. 16. With a corrected seismic record positioned on the 008 periphery of drum 121 of record system 110 and a blank recording 009 tape placed on the periphery of drum 131 of the recording system 010 130 and with master control rod 187 in the illustrated position, 011 the pivotally mounted head moving bar 125 as shown, and the 012 recording head 134 as shown, the record of recording system 120 013 may be sonogrammed with each drum revolution to produce individual 014 traces of an event-selected sonogram record on the recording tape 015 136. After each individual trace is completed, head moving bar 016 125 with pickup heads will be shifted for the production of the 017 next trace until the full sonogram record has been completed.
018 After the complete sonogram record has been produced, 019 the master control rod 187 will be moved from the position shown 020 to a new position, and the recording systems energized a second 021 time. The first trace of the simulated trace record produced in 022 recording system 130 is recorded as the first trace on a blank 023 magnetic tape on the periphery of the drum 161 of recording system 024 160. When all of these traces have been produced, in sequence, 025 the record now recorded on the tape 164 of the recording system 026 160 will be the new improved record in which P-wave and S-wave 027 energy have been separated. And the improved P--wave or S wave 028 record on tape 164 is available for further processing in 029 accordance with the apparatus of FIG. 8.
030 The following patents assigned to the assignee of the 031 present invention which contain sorting and stacking techniques, 032 including beam steering techniques, are of interest in carrying 033 out the method of the present invention.

001 Patent Issued Inventor Title 003 3,597,727 12/30/68 Judson et al Method of Attenua~ing Multiple004 Seismic Signals in the Deter-005 mination of Inline and Cross 006 Dips Employing Cross-Steered 007 Seismic Data 009 3,806,863 4/23/74 Tilley et al Method of Collecting Seismic 010 Data of Strata Underlying 011 Bodies of Water 013 3,638,178 1/25/72 Stephenson Method for Processing Three-014 Dimensional Seismic Data to 015 Select and Plot Said Data on a 016 Two-Dimensional Display Surface 018 3,346,840 10/10/67 Lara Double Sonogramming for Seismic 019 Record Improvement 021 3,766,519 10/16/73 Stephenson Method for Processing Surface 022 Detected Seismic Data to Plot-023 ted Representations of Subsur-024 face Directional Seismic Data 026 3,784,967 1/8/74 Graul Seismic Record Processing 027 Method 029 3,149,302 9/15/74 Klein et al Information Selection Program-030 mer Employing Relative Ampli-031 tude, Absolute Amplitude and 032 Time Coherence 034 3,149,303 9/15/64 Klein et àl Seismic Cross-Section Plotter 036 ~IGS. 17 is a flow diagram illustrative of a computer-037 dominated process in which the functions required by the method of 038 the present invention can be easily ascertained.
039 The steps of FIG. 17 include generating addresses for 040 the P-wave and S-wave refraction data. Variables to be addressed 041 include: refraction amplitude-vs.-time values; offset posi~ion 042 (detector, sourcepoint, centerpoint) sourcepoint-profile number, 043 common offset lines, common centerpoint lines, and common detector 044 location lines, as previously noted. After P-wave and S-wave 04S refraction events have selected and classified, the resulting data 046 are plotted, say, as a function of offset position in the manner 047 of FIG. 9.
048 After the apparent refraction time-vs.-offset data have 049 been displayed and shape of the formation determined as previously 050 suggested, P-wave and S-wave velocity determinations can occur.

~$~7 001 FIG~ 18 illustrates particular elements of a computing 002 system for carrying out the steps of FI~. 17. While many com-003 puting systems are available to carry out the process of the 004 invention, perhaps to best illustra~e operations at the lowest 005 cost per instruction, a microcomputing system 250 is didactically 006 best and is presented in detail below. The system 250 of FIG. 18 007 can be implemented on hardware provided by many different manufac-00~ turers, and for this purpose, elements provided by Intel Corpora-009 tion, Santa Clara, California, may be preferred.
010 Such a system 250 can include a CPU 251 controlled by a 011 control unit 252. Two memory units 253 and 254 connect to the CPU
012 251 through BUS 255. Program memory unit 253 stores instructions 013 for directing the activities of the CPU 251 while data memory unit 014 254 contains data (as data words) related to the seismic data pro-015 vided by the field acquisition system. Since the seismic traces 016 contain large amounts of bit data, an auxiliary memory unit 255 017 can be provided. The CPU 251 can rapidly access data stored 018 through addressing the particular input port, say, at 256 in the 019 Figure. Additional input ports can also be provided to receive 020 additional information as required from usual external equipment 021 well known in the art, e.g., floppy disXs, paper-tape readers, 022 etc., including such equipment interfaced through input interface 023 port 257 tied to a keyboard unit 258 for such devices. Using 024 clock inputs, control circuitry 252 maintains the proper sequence 025 of events required for any processing task. After an instruction 026 is fetched and decoded, the control circuitry issues the appro-027 priate signals (to units both internal and external) for initia-028 ting the proper processing action. Often the control circuitry 029 will be capable of responding to external signals, such as an 030 interrupt or wait request. An interrupt request will cause the 031 control circuitry 252 to temporarily interrupt main program exe-032 cution, jump to a special routine to service the interrupting 001 device, then automatically return to the main program. A wait 002 request is often issued by memory units 253 or 254 c>r an I/O ele-003 ment that operates slower than the CPU.
004 For outputting information, the system 250 can include a 005 printer unit 259 whereby the amplitude of the summed traces as a 006 function of time is printable. Of more use as an output unit, how-007 ever, is disk unit 260, which can temporarily store the data.
008 Thereafter, an off-line digital plotter capable of generating a 009 side-by-side display is used in conjunction with the data on the 010 disk unit 26 0. Such plotters are available in the art, and one 011 proprietary model has been previously described as a computer-012 controlled CRT for optically merging onto photogra~?hic paper, as a 013 display mechanism, the seismic data.
014 FIG. 19 illustrates CPU 251 and control unit 252 in more 015 detail.
016 As shown, the CPU 251 includes an array of registers 017 generally indicated at 262 tied to an ALU 263 through an internal 018 data bus 264 under control of control unit 2520 The registers 262 019 are temporary storage areas. Program counter 265 and instruction 020 register 266 have dedicated uses; the other registers, such as 021 accumulator 26 7, have more general uses.
022 The accumulator 26 7 usually stores one of the seismic 023 operands to be manipulated by the ALU 263. For example, in the 024 summation of traces, the instruction may direct the ALU 263 ~o not 025 only add in sequence the contents of the temporary registers 026 containing predetermined trace amplitudes together with an 027 amplitude value in the accumulator, but also store the result in 028 the accumulator itself. Hence, the accumulator 267 operates as 029 both a source (operand) and a destination tresult) register. The 030 additional registers of the array 262 are useful in manipulation 031 of seismic data, since they eliminate the need to shuffle results 032 back and Eorth between the external memory units of FIG. 18 and ~s~

001 accumulator 267. In practice, most ALU's also provide other built-002 in functions, including hardware subtraction, boolean logic opera-003 tions, and shift capabilities. The ALU 263 also can utilize flag 004 bits generated by FF unit 273 which specify certain conditions 005 that arise in the course of arithmetical and logical manipu-006 lations. Flags typically include carry, zero, sign, and parity.
007 It is possible to progam jumps which are conditionally dependent 008 on the status of one or more flags. Thus, for example, the 009 program may be designed to jump to a special routine if the carry 010 bit is set following an addition instruction.
011 Instructions making up the program for operations involv~
012 ing seismic data are stored in the program memory unit 253 of the 013 CPU 251 of FIG. 18. The program is operated upon in a sequential 014 manner except when instructions in the memory units 253, 254 call 015 for special commands such as "jump" (or "call") instructions.
016 While the program associated with the present invention is a rela-017 tively straightforward one, hence avoiding most "jump" and "call"
018 instructions, "call" instructions for subroutines are common in 019 the processing of seismic data and could be utilized, if desired.
020 In "call" instructions, the CPU 251 has a special way of handling 021 subroutines in order to insure an orderly return to the main pro~
022 gram. ~hen the processor receives a call instruction, it incre-023 ments the program counter 265 and notes the counter's contents in 024 a reserved memory area of the memory unit known as the "stack".
025 CPU's have different ways of maintaining stack contents.
026 Some have facilities for the storage of return addresses built 027 into the CPU itself. Other CPU's use a reserved area of external 028 memory as the stack and simply maintain a "pointer" register, such 029 as pointer register 270, F~G. 19, which contains the address of 030 the most recent stack entry. The stack thus saves the address of 031 the instruction to be executed after the subroutine is completed.
032 Then the CPU 251 loads the address specified in the call into its 001 progam counter 26S. The next instruction fetched will therefore 002 be the first step of the subroutine. The last instruction in any 003 subroutine is a ~return". Such an instruction need specify no 004 address.
005Having now briefly described the operations o~ the CP~
006 251, Table I is presented below containing a full instruction set 007 for its operations.
008TABhE I
009Summary of Processor Instructions by Alphabetical Order 011Instruction Codel _ Clock2 012 Mnemonic Description D7 D~ Ds D4 D3 D2 Dl Do Cycles 014 ACI Add immediate to A
015 with carry 1 1 0 0 1 1 1 0 7 016 ADC M Add memory to A with 017 carry 1 0 0 0 1 1 1 0 7 018 ADC r Add register to A
019 with carry 1 0 0 0 1 S S S 4 020 ADD M Add memory to A 1 0 0 0 0 1 0 1 7 021 ADD r Add register to A 1 0 0 0 0 S S S 4 022 ADI Add immediate to A 1 1 0 0 0 1 1 0 7 023 ANA M And memory with A 1 0 1 0 0 1 1 0 7 024 ANA r And register with A 1 0 1 0 0 S S S 4 025 ANI And immediate with A 1 1 1 0 0 1 1 0 7 026 CALL Call unconditional 1 1 0 0 1 1 0 1 17 027 CC Call on carry 1 1 0 1 1 1 0 011/17 028 CM Call on minus 1 1 1 1 1 1 0 011/17 029 CMA Compliment A 0 0 1 0 1 1 1 1 4 030 CMC Compliment carry 0 0 1 1 1 1 1 1 4 031 CMP M Compare memory with A 1 0 1 1 1 1 1 0 7 032 CMP r Compare register with 034 CNC Call on no carry 1 1 0 1 0 1 0 011/17 035 CNZ Call on no zero 1 1 0 0 0 1 0 011/17 036 CP Call on positive 1 1 1 1 0 1 0 011/17 037 CPE Call on parity even 1 1 1 0 1 1 0 0 11/17 038 CPI Compare immediate 039 with A 1 1 1 1 1 1 1 0 7 040 CPO Call on parity odd 1 1 1 0 0 1 0 0 11/17 041 CZ Call on zero 1 1 0 0 1 1 0 011/17 042 DAA Decimal adjust A 0 0 1 0 0 1 1 1 4 043 DAD B Add B&C to H&L 0 0 0 0 1 0 0 1 10 044 DAD D Add D&E to H&L 0 0 0 1 1 0 0 1 10 045 DAD H Add H&L to H&L 0 0 1 0 1 0 0 1 10 046 DAD SP Add stack pointer to 047 H~L 0 0 1 1 1 0 0 1 10 048 DCR M Decrement memory 0 0 1 1 0 1 0 1 10 049 DCR r Decrememt register 0 0 D D D 1 0 1 5 050 DCX B Decrement B&C 0 0 0 0 1 0 1 1 5 051 DCX D Decrement D&E 0 0 0 1 1 0 1 1 5 052 DCX H Decrement H&L 0 0 1 0 1 0 1 1 5 053 DCX SP Decrement stack 054 pointer 0 0 1 1 1 0 1 1 5 ~ L5~æ7 001 Instruction Codel Clock2 oo32 Mnemonic DescriptionD7 D6 D5 D4 D3 D2 Dl Do C~cles 004 DI Disable interrupt 1 1 1 1 0 0 005 EI Enable interrupts 1 1 1 1 1 0 1 1 4 006 HLT Halt 0 1 1 1 0 1 1 0 7 007 IN Input 1 1 0 1 1 0 1 1 10 008 INR M Increment memory 0 0 1 1 0 1 0 0 10 009 INR r Increment register 0 0 D D D 1 0 0 5 010 INX B Increment B&C
011 registers 0 0 0 0 0 0 1 1 5 012 INX D Increment D&E
013 registers 0 0 0 1 0 0 1 1 5 014 JC Jump on carry 1 1 0 1 1 0 1 0 10 015 JM Jump on minus 1 1 1 1 1 0 1 0 10 016 JMP Jump unconditional 1 1 0 0 0 0 1 1 10 017 JNC Jump on no carry 1 1 0 1 0 0 1 0 10 018 JNZ Jump on no zero 1 1 0 0 0 0 1 0 10 019 JP Jump on positive 1 1 1 1 0 0 1 0 10 020 JPE Jump on parity even 1 1 1 0 1 0 1 0 10 021 JPO Jump on parity odd 1 1 1 0 0 0 1 0 10 022 JZ Jump on zero 1 1 0 0 1 0 1 0 10 023 LDA Load A direct 0 0 1 1 1 0 1 0 13 024 LDAX B Load A indirect 0 0 0 0 1 0 1 0 7 025 LDAX D Load A indirect 0 0 0 1 1 0 1 0 7 026 LHLD Load H&L direct 0 0 1 0 1 0 1 0 16 027 LXI B Load immediate regis-028 ter pair B&C 0 0 0 0 0 0 0 1 10 029 LXI D Load immediate regis-030 ter pair D&E 0 0 0 1 0 0 0 1 10 031 LXI H Load immediate regis-032 ter Pair H&L 0 0 1 0 0 0 0 1 10 033 LXI SP Load immediate stack 034 pointer 0 0 1 1 0 0 0 1 10 035 MVI M ~ove immediate memory 0 0 1 1 0 1 1 0 10 036 MVI r Move immediate 037 register 0 0 D D D 1 1 0 7 038 MOV m,r Move register to 039 memory 0 1 1 1 0 S S S 7 040 MOV r,M Move memory to 041 register 0 1 D D D 1 1 0 7 042 MOV rl,r2 Move register to 043 register 0 1 D D D S S S 5 044 NOP No operation 0 0 0 0 0 0 0 0 4 045 ORA M Or memory with A 1 0 1 1 0 1 1 0 7 046 ORA r Or register with A 1 0 1 1 0 S S S 4 047 ORI Or immediate with A 1 1 1 1 0 1 1 0 7 048 OU~ Output 1 1 0 1 0 0 1 1 10 049 PCHL H&L to program counter 1 1 1 0 1 0 0 1 5 050 POP B Pop register pair B&C
051 off stack 1 1 0 0 0 0 0 1 10 052 POP D Pop register pair D~E
053 off stack 1 1 0 1 0 0 0 1 10 054 POP H Pop register pair H&L
055 off stack 1 1 1 0 0 0 0 1 10 056 POP PSW Pop A and Flags off 057 stack 1 1 1 1 0 0 0 1 10 058 PUSH B Push register Pair 059 B&C on stack 1 1 0 0 0 1 0 1 11 060 PUSH D Push register Pair 061 D&E on stack 1 1 0 1 0 1 0 1 11 062 PUSH H Push register Pair 063 H&L on stack 1 1 1 0 0 1 0 1 11 001 Instruction Codel _ Clock2 002 Mnemonic Descr~ tionD7 D6 D5 D4 D3 Dz Dl Do Cycles 004 PUSH PSW Push A and Flags on 005 stack 1 1 1 1 0 1 0 1 11 006 RAL Rotate A left through 007 carry O O O 1 0 1 1 1 4 008 RAR Rotate A right through 009 carry O O O 1 1 1 1 1 4 010 RC Return on carry 1 1 0 1 1 0 0 05/11 011 RET Return 1 1 0 0 1 0 0 1 10 012 RLC Rotate A Left O O O O O 1 1 1 4 013 RM Return on minus 1 1 1 1 1 0 0 05/11 014 RNC Return on no carry 1 1 0 1 0 0 0 0 5/11 015 RNZ Return on no zero 1 1 0 0 0 0 0 05/11 016 RP Return on positive 1 1 1 1 0 0 0 0 5/11 017 ~PE Return on parity even 1 1 1 0 1 0 0 0 5/11 018 RPO Return on parity odd 1 1 1 0 O O O 0 5/11 019 RRC Rotate A right O O O O 1 1 1 1 4 020 RST Restart 1 1 A A A 1 i 1 11 021 RZ Return on zero 1 1 0 0 1 0 0 05/11 022 SBB M Subtract memory from 023 A with borrow 1 0 0 1 1 1 1 0 7 024 SBB r Subtract register from 025 A with borrow 1 0 0 1 1 S S S 4 026 SBI Subtract immediate from 027 A with borrow 1 1 0 1 1 1 1 0 7 028 SHLD Store H~L direct O O 1 0 0 0 1 0 16 029 SPHL ~&L to stack pointer 1 1 1 1 1 0 0 1 5 030 STA Store A direct O O 1 1 0 0 1 0 13 031 STAX B Store A indirect O O O O O O 1 0 7 032 STAX D Store A indirect O O O 1 0 0 1 0 7 033 STC Set carry O O 1 1 0 1 1 1 4 034 SUB M Subtract memory from A 1 0 0 1 0 1 1 0 7 035 SUB r Subtract register from 037 SUI Subtract immediate 038 from A 1 1 0 1 0 1 1 0 7 039 XCHG Exchange D&E, H&L
040 Registers 1 1 1 0 1 0 041 XRA M Exclusive Or memory 042 with A 1 0 1 0 1 1 1 0 7 043 XRA r Exclusive Or register 044 with A 1 0 1 0 1 S S S 4 045 XRI Exclusive Or immediate 046 with A 1 1 1 0 1 1 1 0 7 047 XTHL Exchange top of stack, 048 H&L 1 1 1 0 0 0 1 1 18 049 lDDD or SSS-OOOB-OOlC~OlOD-OllE~lOOH-lOlL-110 Memory-lllA.
050 2Two possible cycle times (5/11) indicate instruction cycles 051 dependent on condition flags.
052 The method of the present invention provides a geophysi-053 cist with tools for determining shape of formations as well as 054 elastic parameters of interest to indicate likelihood of the forma-055 tion of interest containing ore, marker rock, economic minerals, 056 and the like. However, the invention is not limited to the above-057 described combinations alone. For example, under certain circum-001 tances, it may be desirable to improve resolution of compressional 002 and shear wave events in the records provided by the array of PIG.
003 5.
004 M dification 005 Initially, it should be mentioned that the array 20 of 006 FIG. 5 provides records in which discernment of shear wave and com-007 pressional velocity values is more often than not adequate. But 008 occasionally separation of these values into partic~lar distinct 009 components at each detector Dl, D2 .... f the array 20 of FIG. 5 010 is not possible, since the ray-paths of the shear or compressional 011 waves may not be parallel to one of the axes of response of each 012 detector when the former emerge at each detector station DSl, DS2 013 of FIG. 5. That is to say, if the dip of the reflèctor of the 014 earth formation undergoing survey and critical angle of the 015 refracted waves are such that separation along the axes of 016 response of the detector does occur, then compressional and shear 017 wave arrival times at each detector Dl, D2 -- etc., are usually 018 ascertainable.
019 ~owever, occasionally the ray-paths are not parallel to 020 the response axes of the detectors. Hence, there are components 021 of each in the outputs of two or more of the sub-detectors 300-302 022 of FIG. 20. In FIG. 20, assume that each detector Dl, D2 ..... f 023 FIG. 5 is composed of three sub-detectors 300, 301, 302 whose axes 024 of response are at right angles to each other. In more detail, 025 sub-detector 300 is seen to have an axis of response "V" parallel 026 to vertical arrow 303; sub-detector 301 is known to have an axis 027 of response "T" normal to both the direction of array traverse 304 028 and response axes "V"; while sub-detector 302 is indicated to have 029 an axis of response "R~ parallel to the direction of array 030 traverse 304 but to be normal to both axes of response "V" and "T"
031 of the sub-detectors 300 and 301, respectively.
032 If the compressional or shear ray-path is not parallel 033 to one respective axis of response, i.e., V, R or T, then compo-034 - ~3 -001 nents of both the compressional and shear waves can appear at two 002 or more of the outputs of the sub-detectors 300-302. Such "com-003 bined" traces can be difficult to interpret. That is to say, in 004 FIG. 17 the step of generating correct shear wave velocity and 005 compressional velocity address tags might have been difficult to 006 achieve in those circumstances mentioned above except for the fact 007 that a modification of the present invention is available, as here-008 inafter described.
009 Referring now to FIGS. 21 and 22, there are shown flow 010 diagrams of the modification of the present invention illustrating 011 steps in a computer-dominated process for correctly interpreting 012 detector outputs irrespective of orientation of ray-paths of the 013 emerging shear or compressional waves, the dip of the subterranean 014 reflector or the critical angle of the refracted wave, such detec-015 tor outputs being rapidly and easily interpretable as compres-016 sional or shear-wave, as well as being separately displayed.
017 Generally, as shown in FIG. 21, the process contemplates 018 the following steps:
019 (i) generating address tags for the outputs of each sub-020 detector 300-302 of FIG. 20;
021 (ii) manipulating the addressed data of (i), supra, to gene-022 rate a series of 2-D hodographs in polar coordinates such that a 023 set of V-T, V-R and R-T plots over preselected time gates indicate 024 particle motion, and 025 (iii3 displaying the hodographs, individually or in combi-026 nation, to indicate wave type, vis. either compressional, shear, 027 Rayleigh, etcO, as set forth in detail below.
028 Now in more detail, consider the flow chart of FIG. 22.
029 As shown, the initial four steps of the process are standard pro-030 cedures to the seismic processing industry, viz., (i) initializing 031 and reading of variables of a namelist, (ii) opening the input 032 files; (iii) reading in the master file, and (iv) setting up the 033 - 4~ -001 index and sort array. Then, the main sub-routine is called, viz., 002 "PLHODO" and the 2-D hodographs are generated in the manner set 003 forth below.
004 O~ import in the present aspect of the modification of 005 the invention is the operation of the last-mentioned step of the 006 computer-dominated process, viz. the sub-routine called "PLHODO".
007 Essentially, during this aspect of the present invention, the 008 process is controlled so as to manipulate the addressed traces to 009 generate V-T, V-R and R-T values as a function of time and then to 010 display the resulting plots. In this regard, note that 2-D hodo-011 graphs are defined as plots of particle motion at a specific 012 detector location in which particle motion in two dimensions is 013 plotted as a function of time.
014 Assuming in the case to be described hereinbelow that 015 only two-dimensional hodographs are to be generated, among input 016 values required o~ the program are the usual "standard" parameters:
017 - required space for the traces;
018 - type of array to be used for each trace;
019 - trace identification;
020 - scaling interval;
021 - sampling interval; and 022 - number of traces per scaling interval.
023 After the traces are read into the system set forth in 024 FIG. 18, the computer-dominated system there depicted ~rovides 025 individual trace plots of each detector. Assume that each detec-026 tor is composed of the three fi~ite sub-detectors of FIG. 20, and 027 that the sub-detectors 300-302 have axes of response as shown.
028 From the three separate sub-detectors 300-302, there are 029 provided three separate amplitude-vs.-time traces 306 as shown in 030 FIG. 23, along with rows of two-dimensional hodographs 307. Note 031 that the traces 306 as well as the hodographs 307 appear together 032 as a single display at the output of the processing system of FIG.
033 18. Each two-dimensional hodograph 307 is a ~unction of a time 034 interval, such interval being generated as the amplitude-vs.-time 001 traces are divided into a series of time gates for analysis 002 purposes.
003 In more detail in FIG. 23, across the top of FI~. 23 004 note that separate time gates are indicated, viz. gates 311, 312, 005 313, 314, 315, 316 and 317~ Each gate has a time interval of 006 about 0.20 second. Prior ~o the actual generation of the hodo-007 graphs, note that the interpreter controls the length of each time 008 gate as well as the number of gates to be used per plot. Key to 009 interpretation: gate length and gate numbers are chosen to 010 provide distinguishing characteristics where confusion may occur 011 in interpretation of the original outputs of the detectors. Since 012 refraction studies are usually associated with near-surface 013 phenomena, the last gate 317 of FIG. 23 covers the record interval 014 between 1.6 and 2.0 seconds. Hence, the present invention 015 provides efficient near-surface resolution of data.
016 Additional parameters controlled by the interpreter 017 include: plot scale, length of axes of the plot, type of symbol 018 used, thickness of the for each plot, etc.
019 Next, the twv-dimensional hodographs are actually gene-020 rated as a function of sub-detector output and time. Note in FIG.
021 23 that a series of V-R, V-T and R-T headers generally indicated 022 at 308 appear along the left-hand side of the plot with the 023 particular 2-D hodographs 307 being then displayed across the plot 024 as a function of time. The plots themselves are the data points 02S of the various amplitudes normalized as to both time and plot 026 points, and the two adjacent plot points are connected by a line 027 to provide the depicted hodograph 307O
028 By analysis of the resulting hodographs, the interpreter 029 can determine, with precision, actual values of compressional and 030 shear-wave velocities that have been received at the detector sta 031 tions in the field. In general, in the interpretation of the hodo-032 graphs 307 as provided by the present invention, a few keys should ~5~2~

001 be apparent to those skilled in the art. For example, in the V-R
002 hodographs, Rayleigh and P-wave responses dominate; but in the V-T
003 hodographs, shear waves are most easily seen; and in the R-T hodo-004 graphs, shear waves polarized in vertical or horizontal planes are 005 easily distinguishable over other types of waves. In particular, 006 in FIG. 23, hodographs identified by the number 307a and asso-007 ciated with gate 311, that is, associated with the 0.3-5 second 008 gate indicate that compressional waves are present to almost the 009 total exclusion of any other type of energy. Also note that the 010 hodographs identified by the number 307b associated with gate 317 011 indicate shear waves are present; similarly, the hodographs identi-012 fied by the number 307c associated with gate 315 indicate that 013 Rayleigh waves are present over the particular indicated response 014 period of the sub-detectors.
015 Note further with regard to FIG. 23, that the V, T and R
016 traces 306 are u ually plotted first on a side-by-side basis, 017 followed by the rows of V-R, V-T and R-T hodographs 307 as a func-018 tion of the columnar time gates 311-317. Annotation of the hodo-019 graph axes and time gates usually occurs before the particular 020 tagged data points of the V, T and R traces are converted to plot 021 scale, and the phantom points marked or otherwise indicated in the 022 record. Lastly, lines are drawn through adjacent phantom scaled 023 points to form the hodographs 307 depicted in FIG. 23.
024 Of course, during the interpretation aspects of the 025 invention, the system itself its continuously cross-checking param-026 eters to indicate occurrence of errors in the programming, if any.
027 Lastly, analysis can conclude by the interpretor classi-028 fying particle motion of each hodograph 307 as being horizontal, 029 vertical or circular in the manner of the shear, compressional and 030 Rayleigh wave patterns of FIGS. 4A-4C, supra.
031 A listing of the modifications of the present invention 032 as carried out on the system of FIG. 18, including all the program 033 statements, set forth below.

001 It should thus be understood that the invention is not 002 limited to any specific embodiments set forth herein, as varia-003 tions are readily apparent, and thus the invention is to be given 004 the broadest possible interpretation within the terms of the 005 following claims.

006 - ~8 -

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Method of accurately determining shape and elastic param-eters of an earth formation to identify ore, marker rocks, economic minerals or the like, using a refraction exploration field system including a series of detectors, positioned along a line or survey at inline positions X1, X2, ... Xn and at least one seismic source located adjacent to said detectors for producing a seismic wave for travel through said formation:
(a) generating a seismic wave at a first sourcepoint loca-tion adjacent said series of detectors;
(b) after said wave undergoes refraction, detecting arrival of a refracted wave at said series of detectors at said inline off-set positions, to obtain a first set of traces associated with said offset positions X1, X2, ... Xn;
(c) repeating steps (a) and (b) by generating a second wave at a second sourcepoint adjacent to inline position Xn of said detector positions, and detecting said refracted wave to obtain a second set of traces;
(d) advancing said series of detectors a selected number of inline positions or fractions thereof and repeating steps (a), (b) and (c) above to obtain additional sets of traces, but in which said additional sets of traces are associated with more than two inline positions overlapping common inline positions of said first and second sets of traces;
(e) distinguishing arrival times of shear waves from compres-sional waves by means of two-dimensional hodographs generated by a computer-dominated process; and (f) analyzing arrival times of at least one segment of (i) shear waves and (ii) compressional waves as a function of inline position whereby shape of said earth formation as well as elastic parameters indicative of likelihood of said formation being an ore, marker rock, economic mineral, and the like, are provided.

2. The method of Claim 1 in which step (e) includes the sub-steps of (i) plotting V, T and R amplitude-vs.-time traces on a side-by-side basis to form a record; and (ii) on said record also plotting three separate rows of V-R, V-T and R-T hodographs as a function of a series of columnar time gates, so as to distinguish arrival times of compressional and shear waves associated with and appearing along said side-by-side V, T and R traces.

3. Method of Claim 2 in which sub-step (ii) includes:
(a) annotating both horizontal and vertical axes of said rows of V-R, V-T and R-T hodographs, as well as said columnar time gates; and (b) after converting all trace data points to correct plotter scale, plotting on said record straight lines between said scaled data points, to form said rows of V-R, V-T and R-T hodo-graphs on said record.

4. Method of Claim 3 in which sub-step (ii) includes the additional steps of (c) classifying particle motion associated with said rows of V-R, V-T and R-T hodographs as horizontal, vertical or circular motion; and (d) based on which of said hodographs being classified as horizontal, vertical or circular motion, determining arrival times of said traces as being associated with shear, compressional or Rayleigh waves.

5. In accurately determining shape and elastic parameters of an earth formation to identify ore, marker rocks, economic minerals or the like, using a refraction exploration field system including a series of detectors, positioned along a line of survey at inline positions X1, X2, ... Xn and at least one seismic source located adjacent to said detectors for producing a seismic wave for travel through said formation, means for distinguishing arrival times of refracted shear waves from compressional waves by means of two-dimensional, generated hodographs, and means for plotting a series of said distinguished refracted travel time values versus horizontal offset coordinate annotated by source point-profile number and refraction arrival direction indicated by sourcepoint offset positions at one of a forward and trailing in-line position X1 and Xn of said detectors, slope of said travel time values versus offset being indicative of apparent P-wave and/or S-wave velocities, said sourcepoint offset positions being alignable along an imaginary line of ascertainable slope.

6. Means of Claim 5 in which said distinguishing means includes means for classifying particle motion of said hodographs as vertical, horizontal or circular.

7. Means of Claim 5 in which said plotting means includes means for selecting refraction events from field data provided by said refraction field system, and means for plotting said events to indicate refraction travel time as a formation of horizontal offset.

8. Means of Claim 5 in which said first and second-mentioned means are a properly programmed digital computer.