Three-dimensional imaging of Longmenshan fault using aftershocks of Wenchuan 8.0 earthquake, Sichuan, China
Abstract
We present a three-dimensional (3D) compressional wave speed (Vp), shear wave speed (Vs) and Vp/Vs model for the Longmenshan fault region, Sichuan China, using aftershocks associated with the 2008 Wenchuan 8.0 earthquake. The velocity and ratio models are obtained by a new version of the double- difference seismic tomography method (Zhang, 2003) to simultaneously solve for Vp, Vs, Vp/Vs and event locations. The data used in inversion include 73,013 P arrival times, 62,287 S arrival times and 61,823 S-P travel times recorded by 63 stations on both permanent network and temporary stations in a region 400 km northeast-southwest by 200 km northwest-southeast. The tomographic results show that: (1) in southern segment of Longmenshan fault, the fault is a clear boundary in velocity and Vp/Vs ratio. High P and S velocity and low Vp/Vs ratio exist in western region to the fault, while low velocity and high Vp/Vs ratio in eastern region to the fault, and the Longmenshan fault extends to near 30 km in depth; (2) in northern segment, the general pattern looks like the southern segment, but the Longmenshan fault cuts off a small block with high velocity and low Vp/Vs ratio from western region to the fault with low Vp/Vs ratio; (3) the earthquakes relocated by the joint tomographic inversion collapse to a thin line along the Longmenshan fault, consistent with ground surface ruptures.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.U22B..02P
- Keywords:
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- 8015 Local crustal structure;
- 8180 Tomography (6982;
- 7270)