Deformation on Nearby Faults Induced by the 1999 Hector Mine Earthquake
Interferometric Synthetic Aperture Radar observations of surface deformation due to the 1999 Hector Mine earthquake reveal motion on several nearby faults of the eastern California shear zone.We document both vertical and horizontal displacements of several millimeters to several centimeters across kilometerwide zones centered on pre-existing faults.Portions of some faults experienced retrograde (that is, opposite to their long-term geologic slip) motion during or shortly after the earthquake.The observed deformation likely represents elastic response of compliant fault zones to the permanent co-seismic stress changes. The induced fault displacements imply decreases in the effective shear modulus within the kilometer-wide fault zones, indicating that the latter are mechanically distinct from the ambient crustal rocks.
Additional Information© 2002 American Association for the Advancement of Science. Received for publication 4 June 2002; Accepted for publication 12 August 2002. We thank J. Vidale, P. Segall, and anonymous reviewers for their thoughtful comments. This work was supported by the Southern California Earthquake Center and NSF. Original InSAR data are copyright of the European Space Agency, distributed by Eurimage, Italy, and acquired via the WInSAR Consortium. The ERS SAR imagery was processed using the Caltech/ JPL software package ROI_PAC.
Supplemental Material - FialkoSOM.pdf