Early Postseismic Deformation from the 16 October 1999 Mw 7.1 Hector Mine, California, Earthquake as Measured by Survey-Mode GPS

The 16 October 1999 ( M w 7.1) Hector Mine earthquake was the largest earthquake in California since the 1992 ( M w 7.3) Landers event. The Hector Mine earthquake occurred in the eastern Mojave Desert, where the density of permanent Global Positioning System (GPS) stations is relatively low. Since the earthquake, groups from the United States Geological Survey, University of Southern California, University of California, Los Angeles, University of California, San Diego, and Massachusetts Institute of Technology have made postseismic survey-mode observations to increase the spatial coverage of deformation measurements. A total of 55 sites were surveyed, with markers from a few meters to 100 km from the surface rupture. We present velocity estimates for the 32 sites that had enough repeated observations between 17 October 1999 and 26 March 2000 to provide reliable results; these survey-mode data complement the temporal and spatial coverage provided by newly installed Southern California Integrated Geodetic Network permanent GPS stations and future Interferometric Synthetic Aperture Radar postseismic results. We then use the postseismic velocity estimates to compute a simple afterslip model. Results of inversions show that the observed velocities are consistent with deep afterslip occuring underneath the coseismic rupture area.

[1]  K. Feigl,et al.  Coseismic and Postseismic Fault Slip for the 17 August 1999, M = 7.5, Izmit, Turkey Earthquake. , 2000, Science.

[2]  Kenneth W. Hudnut,et al.  Continuous GPS Observations of Postseismic Deformation Following the 16 October 1999 Hector Mine, California, Earthquake (Mw 7.1) , 2002 .

[3]  J. Zumberge,et al.  Precise point positioning for the efficient and robust analysis of GPS data from large networks , 1997 .

[4]  Kenneth W. Hudnut,et al.  Poroelastic rebound along the Landers 1992 earthquake surface rupture , 1998 .

[5]  Yehuda Bock,et al.  Postseismic deformation following the Landers earthquake, California, 28 June 1992 , 1994, Bulletin of the Seismological Society of America.

[6]  E. Hauksson,et al.  The 1999 Mw 7.1 Hector Mine, California, Earthquake Sequence: Complex Conjugate Strike-Slip Faulting , 2002 .

[7]  James C. Savage,et al.  Postseismic deformation associated with the 1992 M ω=7.3 Landers earthquake, southern California , 1997 .

[8]  P. Segall,et al.  Detection of a locked zone at depth on the Parkfield, California, segment of the San Andreas Fault , 1987 .

[9]  William A. Bryant,et al.  Primary Surface Rupture Associated with the Mw 7.1 16 October 1999 Hector Mine Earthquake, San Bernardino County, California , 2002 .

[10]  Kanamori,et al.  Viscoelastic flow in the lower crust after the 1992 landers, california, earthquake , 1998, Science.

[11]  David T. Sandwell,et al.  Small‐scale deformations associated with the 1992 Landers, California, earthquake mapped by synthetic aperture radar interferometry phase gradients , 1998 .

[12]  Ian Parsons,et al.  Surface deformation due to shear and tensile faults in a half-space , 1986 .

[13]  A. Treiman,et al.  Primary Surface Rupture Associated with the M w 7 . 1 16 October , 2002 .

[14]  Thomas K. Rockwell,et al.  Paleoseismology of the Johnson Valley, Kickapoo, and Homestead Valley Faults: Clustering of Earthquakes in the Eastern California Shear Zone , 2000 .

[15]  Fred F. Pollitz,et al.  Mobility of continental mantle: Evidence from postseismic geodetic observations following the 1992 Landers earthquake , 2000 .

[16]  Duncan Carr Agnew,et al.  Coseismic Displacements from the Hector Mine, California, Earthquake: Results from Survey-Mode Global Positioning System Measurements , 2002 .

[17]  Michael J. Rymer,et al.  Geologic and Paleoseismic Study of the Lavic Lake Fault at Lavic Lake Playa, Mojave Desert, Southern California , 2002 .

[18]  Michael B. Heflin,et al.  The coseismic geodetic signature of the 1999 Hector Mine earthquake , 2000 .

[19]  J. C. Savage.  Equivalent strike‐slip earthquake cycles in half‐space and lithosphere‐asthenosphere earth models , 1990 .