Oct. 26 - Geological Sciences Seminar
(Conferences / Seminars / Lectures)
Dr. Eric Hetland, University of Michigan
"The 2008 Mw 7.9 Wenchuan, China, Earthquake: InSAR, Coseismic Slip, and the Accumulated Stresses"
The 2008 Mw 7.9 Wenchuan, China, Earthquake: InSAR, Coseismic Slip, and the Accumulated Stresses
E.A. Hetland (1), L. Medina Luna (1), and G. Feng(2)
1: Dept. of Earth and Env. Sciences, University of Michigan, Ann Arbor, MI, USA.
2: King Abdllah University of Science and Technology, Thuwal, Kingdom of Saudi ArabiaThe Mw 7.9 Wenchuan earthquake occurred on 12 May 2008, along the middle segment of the Longmen Shan fault zone (LMSfz), marking the eastern margin of the Tibetan plateau and the Sichuan basin in China. The Wenchuan earthquake was devastating to Sichuan Province, with about 70-86 thousand dead and wide-spread damage. The LMSfz is characterized by significant topographic relief indicating that deformation is active, yet prior to the 2008 earthquake this area was fairly seismically quiet and GPS revealed little strain accumulation along the faults. We use ALOS/PALSAR imagery to produce interferometric synthetic aperture radar (InSAR) interferograms of coseismic deformation. We find that many of the radar acquisitions associated with the Wenchuan earthquake were strongly affected by ionospheric disturbances coincident with the rupture. Using InSAR interferograms, as well as GPS data, we investigate the coseismic fault slip that occurred during the 2008 earthquake. The Wenchuan earthquake was oblique-thrust, but coseismic slip models indicate that the fault slip rake varied during the rupture, with progressively more strike-slip occurring on steeper faults as the rupture propagated from the SW to the NE. We further use geodetic-based inferences of coseismic slip to investigate the stresses in the LMSfz that led to the 2008 earthquake, and the relation of these stresses to stain-accumulation. Our initial analysis does not rely on models of static frictional stability, although we are exploring such models in order to seek further constraints on the stresses responsible for the Wenchuan earthquake.