Estimation of rupture processes of the 2008 Wenchuan Earthquake from joint analyses of two regional seismic arrays

We estimated the source rupture of the 2008 Wenchuan Earthquake (Ms 8), China, based on a back-projection of seismic waves to their source plane, using data from regional broadband arrays in Taiwan and northern Vietnam. Observations from these arrays, located at different azimuths, were processed to evaluate the spatio-temporal rupture behavior of the fault. The seismic energy spot converted from windowed array waveforms was back-projected to the rupture plane of the earthquake, to image the instantaneous slip on the fault plane. Rupture processes were reconstructed based on the imaged time-dependent seismic energy radiating from the earthquake fault plane. The high station density of both arrays enabled a detailed examination of the rupture processes. The results indicate that the 2008 Wenchuan Earthquake had a rupture duration of approximately 100. s, with major asperities radiating energy at 50. s after the initiation of rupture. The location of asperities is in good agreement with sections of the earthquake fault along which major damage occurred, such as along the Yingxiu-Beichuan Fault. The radiated seismic energy shows a complex spatial distribution on the fault plane. Our analysis indicates that the rupture initiated at the epicenter and extended to the northeast for approximately 280. km. The average rupture velocity of this earthquake was approximately 2.8. km/s.