3-D joint geodetic and strong-motion finite fault inversion of the 2008 May 12, Wenchuan, China Earthquake

Abstract

SUMMARYWe present a source inversion of the 2008 Wenchuan, China earthquake, using strong-motion waveforms and geodetic offsets together with 3-D synthetic ground motions. We applied the linear multiple time window technique considering geodetic and dynamic Green's functions computed with the finite-element method and the reciprocity and Strain Green's Tensor formalism. All ground motion estimates, valid up to 1 Hz, accounted for 3-D effects, including the topography and the geometry of the Beichuan and Pengguan faults. Our joint inversion has a higher moment (M0) than a purely geodetic inversion and the slip distribution presents differences when compared to 1-D model source inversions. The moment is estimated to be M0 = 1.2 × 1021 N·m, slightly larger than other works. Our results show that considering a complex 3-D structure reduces the size of large areas of 10 m slip or greater by distributing it in wider zones, with reduced slips, in the central portion of the Beichuan and the Pengguan faults. Finally, we compare our source with a relocated aftershock catalogue and conclude that the 4–5 m slip contours approximately bound the absence or presence of aftershocks.