TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 7), pp. e13-e16, 2012


Source process of the 12 May 2008 Wenchuan, China, earthquake determined by waveform inversion of teleseismic body waves with a data covariance matrix

Yuji Yagi1, Naoki Nishimura2, and Amato Kasahara2

1Faculty of Life and Environmental Sciences, University of Tsukuba, Ten'nodai 1-1-1, Tsukuba 305-8572, Japan
2Graduate School of Life and Environmental Sciences, University of Tsukuba, Ten'nodai 1-1-1, Tsukuba 305-8572, Japan

(Received March 2, 2012; Revised May 9, 2012; Accepted May 14, 2012; Online published August 2, 2012)

Abstract: We have estimated the spatio-temporal slip distribution of the 12 May, 2008, Wenchuan earthquake from teleseismic P-wave data. Teleseismic body wave observations are useful geophysical observations for estimating the overall seismic source process immediately after a great earthquake. However, it is difficult to constrain the slip vectors of later sub-events during a large earthquake such as the 2008 Wenchuan earthquake because the modeling error due to the Green's function uncertainty generally increases with time. In this study, we have applied a new waveform inversion method that incorporates the uncertainty of the Green's function, and we have assumed a simple fault plane model to evaluate our inversion scheme for a rapid analysis of the seismic source process. The results show that the slip history of the Wenchuan earthquake include six distinct sub-events. The derived source parameters were a seismic moment M0 = 1.4 × 1021 N m (Mw 8.0) and a source duration = 125 s. The total slip vector distribution and segmentations obtained in our study are consistent with results obtained from InSAR data. The manner of the rupture propagation suggests that the two major source faults, the Beichuan fault and the Pengguan fault, intersected in the deep part of the seismogenic zone.
Key words: Waveform inversion, uncertainty of Green's function, 12 May, 2008, Wenchuan earthquake, seismic source process.

Corresponding author E-mail: yagi-y@geol.tsukuba.ac.jp

[Full text] (PDF 1.8 MB)