HR: 0800h
AN: S51B-0513    [Abstracts]
TI: The rupture velocity of the 2001 Kunlunshan earthquake: A revisit
AU: * Shao, G
EM: shao@umail.ucsb.edu
AF: University of California, Santa Barbara, Department of Earth Sciences UCSB, Santa Barbara, CA 93106, United States
AU: Ji, C
EM: ji@geol.ucsb.edu
AF: University of California, Santa Barbara, Department of Earth Sciences UCSB, Santa Barbara, CA 93106, United States
AB: The rupture processes of the 2001 Kunlunshan earthquake have been studied using seismic and geodetic data. However, there were large discrepancies among previous results, particularly the rupture velocity. The models based on teleseismic P waves generally favored a rupture velocity less or equal to the shear velocity of the upper crust [Antolik, 2004; Ozacar, 2004]. In contrast, the analysis of regional surface waves and teleseismic SH waves support a rupture in 5 to 6 km/sec velocity in at least half of 400 km long rupture plane [Bouchon, 200; Robinson, 2006]. This discrepancy motivated us to explore the uncertainty of the estimated rupture velocity. If we align teleseismic body waves by their arrival times from the hypocenter, the responses from a portion of fault plane turn to follow a straight line, whose slope is the distance to the hypocenter. Then by least-square matching the centroid times of coherent phases, we can determine the locations and rupture times of the corresponding sources. We found that such a method is more precise than the back-projection method. One of the asperities constrained by teleseismic P waves is at 208 km east of the epicenter. Its rupture time is 74 sec, suggesting the lowest average rupture velocity from the hypocenter is about 2.82 km/sec. However, a rupture velocity of 3.9 km/sec would require a rise time larger than 19 sec. We will explore how to reconcile these isolated measurements and the models of finite fault inversions. The slip distributions based on InSAR data and forward spectra element simulation will be used to evaluate the final result.
DE: 7215 Earthquake source observations (1240)
SC: Seismology [S]
MN: 2007 Fall Meeting