Papers by Jeffrey T Freymueller
Geophysical Research Letters, 1997
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ABSTRACT Tectonic and earthquake research in the US has experienced a quiet revolution over the l... more ABSTRACT Tectonic and earthquake research in the US has experienced a quiet revolution over the last decade precipitated by the recognition that slow-motion faulting events can both trigger and be triggered by regular earthquakes. Transient motion has now been found in essentially all tectonic environments, and the detection and analysis of such events is the first-order science target of the EarthScope Project. Because of this and a host of other fundamental tectonics questions that can be answered only with long-duration geodetic time series, the incipient 1400-station EarthScope Plate Boundary Observatory (PBO) network has been designed to leverage 432 existing continuous GPS stations whose measurements extend back over a decade. The irreplaceable recording history of these stations will accelerate EarthScope scientific return by providing the highest possible resolution. This resolution will be used to detect and understand transients, to determine the three-dimensional velocity field (particularly vertical motion), and to improve measurement precision by understanding the complex noise sources inherent in GPS. The PBO Nucleus Project is designed operate, maintain and upgrade a subset of six western U.S. geodetic networks: the Alaska Deformation Array (AKDA), Bay Area Regional Deformation network (BARD), the Basin and Range Geodetic Network (BARGEN), the Eastern Basin and Range/Yellowstone network (EBRY), the Pacific Northwest Geodetic Array (PANGA), and the Southern California Integrated Geodetic Network (SCIGN), until they are subsumed by PBO in 2008. Uninterrupted data flow from these stations will effectively double the time-series length of PBO over the expected life of EarthScope, and create, for the first time, a single GPS-based geodetic network in the US. Other existing sites will remain in operation under support from non-NSF sources (e.g. the USGS), and EarthScope will benefit from their continued operation. On the grounds of relevance to EarthScope science goals, geographic distribution and data quality, 209 of the 432 existing stations have been selected as the nucleus upon which to build PBO. We have begun converting these stations to a PBO-compatible mode of operation; data now flow directly to PBO archives and processing centers while maintenance, operations, and meta-data requirements are currently under upgrade to PBO standards.
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Earth, Planets and Space, 2004
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Journal of Geophysical Research: Solid Earth, 2015
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Nature, Jan 2, 2000
The collision between India and Asia has been simulated with a variety of computational models th... more The collision between India and Asia has been simulated with a variety of computational models that describe or predict the motions of the main faults of east Asia. Geological slip-rate estimates of 20-30 mm yr(-1) suggest that the largest of these faults, the 2,000-km-long Altyn Tagh fault system on the northern edge of the Tibetan plateau, absorbs as much of the Indo-Asian convergence signal as do the Himalayas--partly by oblique slip and partly by contraction and mountain growth. However, the predictions of dynamic models for Asian deformation and the lower bounds of some geological slip-rates estimates (3-9 mm yr(-1); refs 7, 8) suggest that the Altyn Tagh system is less active. Here, we report geodetic data from 89-91 degrees E that indicate left-lateral shear of 9 +/- 5 mm yr(-1) and contraction of 3 +/- 1 mm yr(-1) across the Altyn Tagh system. This result--combined with our finding that, at 90 degrees E, Tibet contracts north-south at 9 +/- 1 mm yr(-1)--supports the predicti...
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Eos, Transactions American Geophysical Union, 2000
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Okmok volcano is located on Umnak Island in the Aleutian Arc, Alaska. This volcano consists of a ... more Okmok volcano is located on Umnak Island in the Aleutian Arc, Alaska. This volcano consists of a large caldera, and there are several post-caldera cones within the caldera. It has erupted more than 10 times during the last century, with the latest eruption occurring in February 1997. Annual GPS campaigns during 2000-2003 have revealed a rapid inflation at Okmok volcano.
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InSAR is a satellite based radar technique capable of measuring small ground displacements at hig... more InSAR is a satellite based radar technique capable of measuring small ground displacements at high spatial resolution and, due to the look angle of the satellites used, is especially sensitive to vertical displacements. By combining images taken from different directions, and by using independent measurements of horizontal displacements (e.g. GPS, image matching), it is possible to measure the vertical component
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We investigate the processes of postseismic deformation following the 2002 Denali Fault, Alaska e... more We investigate the processes of postseismic deformation following the 2002 Denali Fault, Alaska earthquake using 4.5 years of continuous and campaign GPS data. Afterslip is modeled on a fault in an elastic lithosphere overlying a Maxwell (linear) viscoelastic asthenosphere. We assume afterslip is governed by a nonlinear velocity- strengthening friction law. Postseismic GPS time-series are best explained by a combination
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Eos, Transactions American Geophysical Union, 1998
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The M7.9 2002 Denali Fault earthquake, Alaska is one of the largest strike-slip earthquakes ever ... more The M7.9 2002 Denali Fault earthquake, Alaska is one of the largest strike-slip earthquakes ever recorded. A large array of GPS receivers measured the postseismic response and several mechanisms, including viscoelastic flow, afterslip, lower crustal flow and poroelastic rebound, have been used to model the data (e.g. Freed et al, 2006). However, despite the sizeable GPS array, there are still
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Papers by Jeffrey T Freymueller