Interferometric Synthetic Aperture Radar (InSAR) imaging of crustal deformation associated with the May 2009 earthquake sequence in northwestern Saudi Arabia
Abstract
An earthquake swarm that occurred in May 2009 in the NW Saudi Arabia provides an opportunity to study a likely dike intrusion event that may characterize rifting-related processes associated with the central Red Sea region. The earthquake sequence culminated in the shallow, Mw 5.7 earthquake on May 19, and the reported moment tensor solutions depict NW-SE striking normal faulting. This study uses Interferometric Synthetic Aperture Radar (InSAR) to assess surface deformation associated with the earthquake swarm. Using a combination of data from Envisat ASAR and ALOS PALSAR, we construct a sparse time series of deformation spanning the earthquake swarm and the subsequent four months. The results demonstrate that minimal deformation occurred in the area during the preceding two years, and that approximately 0.80 m of vertical displacement was associated with the earthquake swarm in May 2009. The resulting displacement maps also demonstrate two local peaks that may correspond with localized deformation associated with inflation and deflation of shallow magma chambers. During the subsequent two months, an additional ~0.15 m of vertical displacement occurred. Using elastic dislocation models to infer fault parameters, the displacements are best fit using a tensile crack and two point sources - i.e., fault parameters more characteristic of a dike intrusion, rather than shear faulting. The resulting estimate of geodetic moment (~4 x 1022 N m) is more than an order of magnitude larger than the reported seismic moment. In the large, regional context, this event may exemplify the tectonic processes that are building the incipient passive margin of the Red Sea. Additionally, InSAR provides a means of monitoring subsequent ground deformation and modeling the evolving stress changes in the upper crust, which, in turn, will help reassess the volcanic and seismic hazard associated in the area.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.T51C1535G
- Keywords:
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- 1240 GEODESY AND GRAVITY / Satellite geodesy: results;
- 7230 SEISMOLOGY / Seismicity and tectonics;
- 8109 TECTONOPHYSICS / Continental tectonics: extensional