Crustal deformation across the Imperial Fault: Results from kinematic GPS surveys and trilateration of a densely spaced, small‐aperture network

Genrich, J. F.; Bock, Yehuda; Mason, R. G.

doi:10.1029/96jb02854

Cited by 24 publications

(26 citation statements)

References 30 publications

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“…Thus creep may occur on segments where most of the stress is supported at shallow depths [Savage and Lisowski, 1993]. Our model demonstrates such behavior in the Imperial region, the Brawley seismic zone, and the Calaveras segment, where shallow creep has been known to occur [Genrich and Bock, 1997;Bakun, 1999;Lyons et al, 2002]. We also note that while the Parkfield segment is found to have moderate locking depth (14 km) in our analysis, it also demonstrates high shallow stress accumulation.…”

Section: Coulomb Stress and Fault Creepmentioning

confidence: 57%

“…Published values of locking depth for the Imperial fault range from 8 to 13 km [Archuleta, 1984;Genrich and Bock, 1997;Lyons et al, 2002], typically accompanying 45 mm/yr of slip with variations of surface creep. Genrich and Bock [1997] argue for a 9 km locking depth but also cite 5 km as a reasonable minimum. Seismicity locations are identified at depths of 7.5 km ± 4.5 km [Richards-Dinger and Shearer, 2000], lending equal validity to our more shallow locking depth estimate.…”

Section: B1 Profile 1 Segmentmentioning

confidence: 99%

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Coulomb stress accumulation along the San Andreas Fault system

Smith

Sandwell

2003

J. Geophys. Res.

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[1] Stress accumulation rates along the primary segments of the San Andreas Fault system are computed using a three-dimensional (3-D) elastic half-space model with realistic fault geometry. The model is developed in the Fourier domain by solving for the response of an elastic half-space due to a point vector body force and analytically integrating the force from a locking depth to infinite depth. This approach is then applied to the San Andreas Fault system using published slip rates along 18 major fault strands of the fault zone. GPS-derived horizontal velocity measurements spanning the entire 1700 Â 200 km region are then used to solve for apparent locking depth along each primary fault segment. This simple model fits remarkably well (2.43 mm/yr RMS misfit), although some discrepancies occur in the Eastern California Shear Zone. The model also predicts vertical uplift and subsidence rates that are in agreement with independent geologic and geodetic estimates. In addition, shear and normal stresses along the major fault strands are used to compute Coulomb stress accumulation rate. As a result, we find earthquake recurrence intervals along the San Andreas Fault system to be inversely proportional to Coulomb stress accumulation rate, in agreement with typical coseismic stress drops of 1-10 MPa. This 3-D deformation model can ultimately be extended to include both time-dependent forcing and viscoelastic response.

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Section: Coulomb Stress and Fault Creepmentioning

confidence: 57%

Section: B1 Profile 1 Segmentmentioning

confidence: 99%

Coulomb stress accumulation along the San Andreas Fault system

Smith

Sandwell

2003

J. Geophys. Res.

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“…One of the base stations (HOLT) was then tightly constrained and all site data was processed epoch‐by‐epoch relative to the base station network. Unlike Genrich et al [1997], we processed all of the survey data using instantaneous positioning (discussed above and in the work of Bock et al [2000]) rather than the batch least squares method. We defined anomalous solutions as three times the interquartile range and removed these points from the suite of position estimates at each site.…”

Section: Methodsmentioning

confidence: 99%

“…Most of the motion from these earthquakes has occurred along the Imperial Fault, a right‐lateral strike‐slip fault which runs for 69 km through the eastern portion of El Centro and the western side of Holtville, south into the Mexicali Valley (Figure 1). A relatively fast‐moving fault, the estimated average slip rate along the Imperial Fault ranges from 15–20 mm yr −1 based on shoreline deposits [ Thomas and Rockwell , 1996] to 35–43 mm yr −1 based on conventional geodetic surveys [ Bennett et al , 1996; Genrich et al , 1997; Wdowinski et al , 2001]. Geodetic rates indicate the Imperial Fault accommodates almost 80% of the total plate motion between the North American and Pacific Plates.…”

Section: Introductionmentioning

confidence: 99%

“…Along the Imperial Fault, studies of pre‐1979‐earthquake slip rates using creep meter measurements [ Goulty et al , 1978; Cohn et al , 1982; Louie et al , 1985] yielded only 2–5 mm yr −1 of fault creep. However, using EDM surveys of fault‐crossing lines, Genrich et al [1997] found an average of 10–14 mm yr −1 of creep between 1987 and 1993. They attributed this high rate to triggered slip from the 1987 Superstition Hills earthquake, which would imply that current rates would be closer to pre‐1979 estimates.…”

Section: Introductionmentioning

confidence: 99%

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Creep along the Imperial Fault, southern California, from GPS measurements

2002

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In May of 1999 and 2000, we surveyed with Global Positioning System (GPS) 46 geodetic monuments established by Imperial College, London, in a dense grid (half‐mile spacing) along the Imperial Fault, with three additional National Geodetic Survey sites serving as base stations. These stations were previously surveyed in 1991 and 1993. The Imperial College sites were surveyed in rapid‐static mode (15–20 min occupations), while the NGS sites continuously received data for 10 h d−1. Site locations were calculated using the method of instantaneous positioning, and velocities were determined relative to one of the NGS base stations. Combining our results with far‐field velocities from the Southern California Earthquake Center (SCEC), we fit the data to a simple elastic dislocation model with 35 mm yr−1 of right‐lateral slip below 10 km and 9 mm yr−1 of creep from the surface down to 3 km. The velocity field is asymmetrical across the fault and could indicate a dipping fault plane to the northeast or a viscosity contrast across the fault.

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GNSS Geodesy in Geophysics, Natural Hazards, Climate, and the Environment

Bock

Wdowinski

2020

Position, Navigation, and Timing Technologies in the 21st Century

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Crustal deformation across the Imperial Fault: Results from kinematic GPS surveys and trilateration of a densely spaced, small‐aperture network

Cited by 24 publications

References 30 publications

Coulomb stress accumulation along the San Andreas Fault system

Coulomb stress accumulation along the San Andreas Fault system

Creep along the Imperial Fault, southern California, from GPS measurements

GNSS Geodesy in Geophysics, Natural Hazards, Climate, and the Environment

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