Elisa Zuccolo

Earthquake early warning (EEW) is becoming an increasingly attractive real-time strategy for mitigating the threats posed by potentially devastating incoming seismic events. As efforts accelerate to develop practical EEW-based solutions for earthquake-prone countries in Europe, it is important to understand and quantify the level of performance that can be achieved by the underlying seismological algorithms. We conduct a conceptual study on EEW performance in Europe, which explicitly focuses on the accuracy and associated uncertainties of selected methodological approaches. Twenty-three events from four diverse European testbeds are used to compare the quality of EEW predictions produced by the Virtual Seismologist and PRobabilistic and Evolutionary early warning SysTem algorithms. We first examine the location and magnitude estimates of the algorithms, accounting for both bias and uncertainty in the resulting predictions. We then investigate the ground-shaking prediction capabiliti...

ABSTRACT We illustrate an operational neo-deterministic approach that allows for the definition of time dependent scenarios of ground shaking, through the routine updating of earthquake predictions. The integrated procedure for seismic input definition, which is currently applied to the Italian territory, combines different pattern recognition techniques, designed for the space-time identification of strong earthquakes, with algorithms for the realistic modeling of ground motion. Accordingly, a set of neo-deterministic scenarios of expected ground motion, associated with the alarmed areas, is defined by means of full waveform modeling, both at regional and local scale. The space and time constraints about the impending strong earthquakes are provided by three formally defined and globally tested algorithms, which have been developed according to a pattern recognition scheme. Two algorithms, namely CN and M8S (i.e. a spatially stabilized variant of M8), are routinely used for intermediate-term middle-range earthquake predictions, while the third algorithm allows for the time-independent identification of the areas prone to large events. The pattern recognition of earthquake-prone areas (i.e. seismogenic nodes) does not belong to the family of earthquake prediction algorithms, since it does not provide any information about the time of occurrence of the expected earthquakes; nevertheless, it can be considered as the term-less zero-approximation, which restrains the alerted areas (e.g. defined by CN or M8S) to the more precise location of large events. An intermediate-term middle-range earthquake prediction experiment is ongoing since 2003, aimed at a real-time testing of M8S and CN predictions for earthquakes with magnitude larger than a given threshold (namely 5.4 and 5.6 for CN algorithm, and 5.5 for M8S algorithm) in the Italian region and its surroundings. Predictions are regularly updated every two months and a complete archive of predictions is made available on-line (http://www.ictp.trieste.it/www_users/sand/prediction/prediction.htm); the results obtained during about six years of real-time testing already permitted a preliminary assessment of the significance of the issued predictions. According to the integrated neo-deterministic procedure, the ground shaking scenarios associated with the alerted area are defined, based on the possibility to compute complete synthetic seismograms by the modal summation technique, considering altogether the set of possible sources included in the alarmed region. Examples of neo-deterministic scenarios are provided, at regional and local scale and for sites where the knowledge of the local geological conditions permitted a detailed evaluation of the expected ground motion. The time-dependent ground motion scenarios, associated to the alarmed areas, are regularly updated every two months since January 2008, thus providing an operational tool for defining priority of prevention and mitigation actions.

On May 20, 2012, a seismic event of moment magnitude MW = 6.1 hit and caused severe damage on a large area in the river Po Valley, located in the northern Italy. This earthquake was characterized by extensive occurrence of soil liquefaction and basin effects lying over deep deposits. Within the scope of the European research project titled LIQUEFACT, a reference site located in the countryside near the hamlet of Pieve di Cento (at the boundary of the province of Bologna towards Ferrara) was selected as a trial field in order to assess the effectiveness of several mitigation measures against liquefaction. As a first step of the task, this paper presents the geotechnical model of the site based on in-situ investigations and pre-existing geological studies, which allowed to locate the bedrock depth. As a second step, representative input motions for the LIQUEFACT project were selected aiming at simulating the 20.V.2012 seismic event as well as three possible future scenarios with an in...

Central Asia is one of the seismically most active regions in the world. Its complex seismicity due to the collision of the Eurasian and Indian plates has resulted in some of the world’s largest intra-plate events over history. The region is dominated by reverse faulting over strike slip and normal faulting events. The GSHAP project (1999), aiming at a hazard assessment on a global scale, indicated that the region of Central Asia is characterized by peak ground accelerations for 10 % probability of exceedance in 50 years as high as 9 m/s2. In this study, carried out within the framework of the EMCA project (Earthquake Model Central Asia), the area source model and different kernel approaches are used for a probabilistic seismic hazard assessment (PSHA) for Central Asia. The seismic hazard is assessed considering shallow (depth < 50 km) seis-micity only and employs an updated (with respect to previous projects) earthquake catalog for the region. The seismic hazard is calculated in

Performance of a novel low-magnitude regional ground-motion prediction equation (GMPE) is assessed in the paper by comparing GMPE predictions with independent ground-motion data and other regional, European, and global GMPEs through the log-likelihood method. The novel GMPE was developed using 2270 waveforms coming from 319 earthquakes occurred in Southern Italy till the end of year 2014, with local magnitudes ranging between 1.5 and 4.2, recorded at 60 stations with hypocentral distances varying from 3 km to about 100 km. This GMPE is able to predict peak ground acceleration and 5% damped spectral acceleration at 11 oscillator periods ranging from 0.1 to 3 s with reference to stiff ground conditions (i.e. ground category B according to the Italian Building Code and Eurocode 8). The GMPE coefficients were computed through a nonlinear weighted damped least-squares algorithm, attributing a higher weight to accelerometric data recorded at stations whose soil category was defined using ...

A feasibility study of an earthquake early warning (EEW) system was conducted for Antigua & Barbuda (Eastern Caribbean Region) testing two interface earthquake scenarios corresponding to the maximum credible earthquake and to the earthquake scenario associated with a return period of 475 years. Broadband synthetic seismograms were produced at three selected sensitive facilities, where there is possible interest in the installation of an EEW system. The expected damage was retrieved from the synthetic seismograms and compared with the lead-time determined for a regional EEW, configured to a first approximation based on the principles of geometrical optics. Next, the Virtual Seismologist EEW algorithm, as included in SeisComp3, was tested. Additional broadband synthetic seismograms were produced for the stations in the Eastern Caribbean seismic networks in order to simulate the real time behaviour of the seismic networks during the occurrence of the synthetic earthquakes and to assess...

Central Asia is one of the seismically most active regions in the world. Its complex seismicity due to the collision of the Eurasian and Indian plates has resulted in some of the world’s largest intra-plate events over history. The region is dominated by reverse faulting over strike slip and normal faulting events. The GSHAP project (1999), aiming at a hazard assessment on a global scale, indicated that the region of Central Asia is characterized by peak ground accelerations for 10% probability of exceedance in 50 years as high as 9 m/s2. In this study, carried out within the framework of the EMCA project (Earthquake Model Central Asia), the area source model and different kernel approaches are used for a probabilistic seismic hazard assessment (PSHA) for Central Asia. The seismic hazard is assessed considering shallow (depth < 50 km) seismicity only and employs an updated (with respect to previous projects) earthquake catalog for the region. The seismic hazard is calculated in t...

In this paper, we present an open-source end-to-end Python tool for ground motion record selection and scaling for non-linear dynamic analysis of structures. The tool, named haselREC (HAzard-based SELection of RECords), has been formulated to be executed after performing a probabilistic seismic hazard and disaggregation analysis with OpenQuake, an open-source hazard and risk calculation engine developed by the Global Earthquake Model (GEM) Foundation. In addition to common intensity measures, such as peak ground acceleration and spectral acceleration, haselREC can perform ground motion record selection using average spectral acceleration, which can be advantageous when assessing multiple structures and to account for uncertainty on the conditioning response period. Moreover, haselREC can be directly linked to the web services of the European Strong Motion database for automatic download and scaling of records. The Python tool was designed to be modular, which facilitates its integration in third party scripts for automated record selection and scaling in hazard analysis studies. Here, we describe the main features of the software package in detail and provide an application example for the regional assessment of existing bridge structures.

This paper presents a geospatial methodology for zoning the earthquake-induced soil liquefaction risk at a continental scale and set-up in a Geographic Information System (GIS) environment by coupling data-driven and knowledge-driven approaches. It is worth mentioning that liquefaction is a phenomenon of soil instability occurring at a very local spatial scale; thus, the mega-zonation of liquefaction risk at a continental scale is a hard facing challenge. Since the risk from natural disasters is the convolution of hazard, vulnerability, and exposure, the liquefaction risk mapping is based on the combination of geospatial explanatory variables, available at the continental scale, of the previously listed three assumed independent random variables. First, by applying a prediction model calibrated for Europe, the probability of liquefaction is mapped for the whole continent. Then, the Analytical Hierarchy Process (AHP) is adopted to identify areas that have a high risk of liquefaction,...

Abstract We present the results of the numerical simulation of the May 29, 2012 Emilia Romagna earthquake in Northern Italy using an approach that computes synthetic seismograms associated to earthquake scenarios by combining broadband synthetic seismograms (0–10 Hz) obtained using the UCSB broadband code with nonlinear ground response analyses carried out using the program NOAH. The comparison with the recorded waveforms allowed validating the predictive capability of the adopted method in the proximity of the epicenter. The main limitation of the study is the inappropriateness of 1D modeling in a region characterized by a steep variation of the roof of the buried bedrock.

ABSTRACT A low‐magnitude regional ground‐motion prediction equation (GMPE) for peak ground acceleration and 5% damped spectral acceleration at 11 oscillator periods ranging from 0.1 to 3 s was developed for applications of the earthquake early warning system operating in southern Italy. The accelerometric dataset was built out of 2270 waveforms from 319 earthquakes with local magnitude ranging from 1.5 to 4.2, recorded from 60 stations located on soil type B, according to the Italian Building Code and Eurocode 8, with hypocentral distances ranging from 3 to about 100 km. The GMPE coefficients were computed through a nonlinear weighted damped least‐squares algorithm, attributing a higher weight to ground‐motion data recorded at stations for which soil category was established using geotechnical and geophysical measurements. Predictions of the proposed GMPE were tested against independent ground‐motion data recorded in southern Italy and compared with other regional and global GMPEs through the log‐likelihood method. The comparison shows that the proposed GMPE performs better than any other GMPE considered in this study.

ABSTRACT The definition of realistic seismic input can be obtained from the computation of a wide set of time histories, corresponding to possible seismotectonic scenarios. The propagation of the waves in the bedrock from the source to the local laterally varying structure is computed with the modal summation technique, while in the laterally heterogeneous structure the finite difference method is used. The definition of shear wave velocities within the soil cover is obtained from the non-linear inversion of the dispersion curve of group velocities of Rayleigh waves, artificially or naturally generated. Information about the possible focal mechanisms of the sources can be obtained from historical seismicity, based on earthquake catalogues and inversion of isoseismal maps. In addition, morphostructural zonation and pattern recognition of seismogenic nodes is useful to identify areas prone to strong earthquakes, based on the combined analysis of topographic, tectonic, geological maps and satellite photos. We show that the quantitative knowledge of regional geological structures and the computation of realistic ground motion can be a powerful tool for a preventive definition of the seismic hazard in Italy. Then, the formulation of reliable building codes, based on the evaluation of the main potential earthquakes, will have a great impact on the effective reduction of the seismic vulnerability of Italian urban areas, validating or improving the national building code.

A feasibility study of an earthquake early warning (EEW) system was conducted for the Eastern Caribbean region using scenario earthquakes, corresponding to the maximum credible earthquakes and to the earthquakes associated with a return period of 475 years. Broadband synthetic seismograms were produced at selected critical facilities, where there is potential interest in the installation of an EEW system. The expected damage was derived from the synthetic seismograms and compared with the lead-time determined for both a regional and on-site EEW configuration. Next, the Virtual Seismologist EEW algorithm, as included in SeisComP3, was tested. Additional broadband synthetic seismograms were produced for the stations in the Eastern Caribbean seismic networks in order to simulate the real time behaviour of the seismic networks during the occurrence of the synthetic earthquakes and to assess the predictive capacity of the selected ground motion prediction equation. Expected peak ground parameters and lead-times at the critical facilities constitute the major outcome of the study.

Central Asia has a long history of large to moderate frequent seismicity and is therefore considered one of the most seismically active regions with a high hazard level in the world. In the hazard map produced at global scale by GSHAP project in 1999(Giardini, 1999), Central Asia is characterized by peak ground accelerations with return period of 475 years as high as 4.8 m/s2. Therefore Central Asia was selected as a target area for EMCA project (Earthquake Model Central Asia), a regional project of GEM (Global Earthquake Model) for this area. In the framework of EMCA, a new generation of seismic hazard maps are foreseen in terms of macro-seismic intensity, in turn to be used to obtain seismic risk maps for the region. Therefore Intensity Prediction Equation (IPE) had been developed for the region based on the distribution of intensity data for different earthquakes occurred in Central Asia since the end of 19th century (Bindi et al. 2011). The same observed intensity distribution h...

In recent years, new approaches for developing earthquake rupture forecasts (ERFs) have been proposed to be used as an input for probabilistic seismic hazard assessment (PSHA). Zone- based approaches with seismicity rates derived from earthquake catalogs are commonly used in many countries as the standard for national seismic hazard models. In Italy, a single zone- based ERF is currently the basis for the official seismic hazard model. In this contribution, we present eleven new ERFs, including five zone-based, two smoothed seismicity-based, two fault- based, and two geodetic-based, used for a new PSH model in Italy. The ERFs were tested against observed seismicity and were subject to an elicitation procedure by a panel of PSHA experts to verify the scientific robustness and consistency of the forecasts with respect to the observations. Tests and elicitation were finalized to weight the ERFs. The results show a good response to the new inputs to observed seismicity in the last few c...

Seismic hazard assessment can be performed in various ways, following probabilistic or deterministic approaches. The probabilistic analysis, on which is based the new Italian seismic code, is formally inaccurate, since it relies on convolutive techniques and approximations in the calculation process, which cannot be rigorously applied and that may lead to unrealistic results. These basic formal pitfalls of the probabilistic approach are overcome when resorting to the neo-deterministic approach, which is based on the calculation of synthetic seismograms and hence does not require the mentioned, often not valid, approximations. From a factual point of view, probabilistic hazard assessment performances proved to be very unsatisfactory by recent destructive earthquakes. On the other side, neo-deterministic hazard maps have been satisfactorily compared with observations available so far. Moreover recent earthquakes occurred in the areas where neo-deterministic maps were available, succes...

The 3 January 1117 earthquake (I0 at least IX MCS) is the largest known event occurred so far in the Po Valley. Although its effects were felt in a vast area of northern Italy the source characteristic of this event are still poorly understood and strongly debated. The re-evaluation of historical earthquakes is an important task in seismic hazard assessment studies in order to better understand the past events and to prevent future damage. For the 1117 earthquake a parametric analysis on the source main characteristics (magnitude, epicenter, ipocentral depth and focal mechanism) has been done computing different scenarios of expected ground motion, which are defined by means of full waveform modeling (neo-deterministic approach). These parameters have been varied inside a range of possible values chosen according to the re-evaluation appeared in recently published literature, the instrumental seismic recordings for the small magnitude earthquakes in the zone and the seismogenic zone...

E. Zuccolo, M. Corigliano, CG Lai, F. Bozzoni, L. Scandella, W. Salazar GNGTS – 29° Convegno Nazionale Prato 26-29 ottobre 2009 ... 2 Zuccolo, Corigliano, Lai, Bozzoni, Scandella, Salazar Zone-free approach applied to subduction zone in the Eastern Caribbean Islands 2 ...

ABSTRACT This article illustrates the results of a study aimed at developing a methodology for the automatic identification of the seismic input at outcropping rock sites and flat topographic conditions necessary to carry out non-linear dynamic analysis of structures and geotechnical systems. The seismic input is provided in terms of a set of 7 natural accelerograms recorded on outcropping rock and satisfying the average spectral compatibility requirements prescribed by the Italian seismic code (NTC08). The study focuses on the territory encompassing Tuscany region in Central Italy and it has been carried out for six return periods, which are 50, 75, 101, 475, 712 and 949 years. The procedure involved four main steps: (1) grouping of the response spectra with similar features; (2) definition of the reference response spectrum for each group; (3) selection of spectrum-compatible accelerograms using the reference response spectrum of each group; and (4) linear scaling of the accelerograms to satisfy the compatibility requirement with respect to other response spectra of the group. The last step is implemented through an interactive, user-friendly program named SCALCONA 2.0, which provides the seismic input in agreement with the site location and return period specified by the user. The program is freely available at the following web site: http://www.rete.toscana.it/sett/pta/sismica/01informazione/banchedati/input_sismici/progettazione/index.htm.

An advanced modeling technique that allows us to compute realistic synthetic seismograms was used to create a database of realistic synthetic accelerograms in a set of selected sites in the Sofia urban area. The accelerograms can be used to assess the local site response in terms of the response spectra ratio (RSR). The results of this study, i.e. time histories,

... Examples of neo-deterministic scenarios are provided at regio-nal and local scales considering the cities of Trieste and Nimis (Friuli Venezia Giulia region, NE Italy) where the knowledge of the geological conditions permitted a detailed evaluation of the expected ground motion ...

Estimates of seismic hazard obtained using the neo-deterministic approach (NDSHA) and the probabilistic approach (PSHA) are compared for the Italian territory. The NDSHA provides values larger than those given by the PSHA in areas where large earthquakes are observed and in areas identified as prone to large earthquakes, but lower values in low-seismicity areas. These differences suggest the adoption of the flexible, robust and physically sound NDSHA approach to overcome the proven shortcomings of PSHA, thus allowing for a reliable seismic hazard estimation, especially for those areas characterized by a prolonged quiescence, i.e. in tectonically active sites where events of only moderate size have occurred in historical times.

ABSTRACT A representation of seismic hazard is proposed for Italy based on the zone-free approach developed by Woo (BSSA 86(2):353–362, 1996a), which is based on a kernel estimation method governed by concepts of fractal geometry and self-organized seismicity, not requiring the definition of seismogenic zoning. The purpose is to assess the influence of seismogenic zoning on the results obtained for the probabilistic seismic hazard analysis (PSHA) of Italy using the standard Cornell’s method. The hazard has been estimated for outcropping rock site conditions in terms of maps and uniform hazard spectra for a selected site, with 10 % probability of exceedance in 50 years. Both spectral acceleration and spectral displacement have been considered as ground motion parameters. Differences in the results of PSHA between the two methods are compared and discussed. The analysis shows that, in areas such as Italy, characterized by a reliable earthquake catalog and in which faults are generally not easily identifiable, a zone-free approach can be considered a valuable tool to address epistemic uncertainty within a logic tree framework.

This paper deals with the neo-deterministic definition of the seismic input in the municipality of Nimis (Italy), aimed at the design of residential seismically isolated buildings. The seismic input is defined by the computation of realistic synthetic seismograms considering different ...

ABSTRACT The Italian building code defines the seismic action in terms of elastic acceleration response spectra derived from the results of a probabilistic seismic hazard study performed for the whole national territory. This representation of the seismic input is insufficient for several situations (e.g. analysis of geotechnical systems or time-history analyses of structures), for which the seismic input needs to be specified in terms of accelerograms. This work illustrates a methodology for the seismic mesozonation of the Italian territory, with the aim of defining suites of 7 real accelerograms recorded at outcropping rock sites with flat topographic conditions and, most importantly, compatible with the elastic acceleration response spectrum defined by the Italian building code at any location in Italy. These accelerograms do not require any correction and can be directly used for nonlinear dynamic analyses of structures and geotechnical systems. The mesozonation is based on identification of groups of spectra with similar characteristics and shape. For each of these groups, a parent spectrum is defined and used for selecting real spectrum-compatible records. Limited linear scaling is then applied to these accelerograms to make them compatible with all the response spectra of the group. The results of this work for the 475-years return period are accessible through the SEISM-HOMEWeb-GIS (www.eucentre.it/seismhome.html) providing, for any site in Italy, a suite of 7 real accelerograms spectrum-compatible, on average, with the acceleration response spectrum prescribed by the Italian building code. SEISM-HOME is a useful tool for practitioners needing ready-to-use time-histories for seismic analyses.

ABSTRACT The city of Sofia has the densest population of Bulgaria — around 1.27 million people. The capital is exposed to high seismic risk. According to the Bulgarian seismic code, Sofia has been included in a seismic category characterized by intensity IX (MSK), which corresponds to a horizontal acceleration of 0.27 g for the anchoring of the elastic response spectrum. Because of the lack of instrumental seismic data, realistic synthetic strong motion waveforms for two opposite positions of seismic sources, have been generated for an expected earthquake scenarios (M = 7) along three geological profiles. A hybrid modeling method has been used for the modeling, which is based on the modal summation technique and finite difference scheme. The calculation has been done using an extended source model. The site effect is represented in terms of response spectra ratio (RSR), with respect to a bedrock model. The three components synthetic seismograms, computed in the domain of displacement, velocity and acceleration have been processed to extract some parameters very useful for engineering applications.