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International Journal of Geophysics
Volume 2011, Article ID 216315, 13 pages
http://dx.doi.org/10.1155/2011/216315
Research Article

Seismic Imaging and Seismicity Analysis in Beijing-Tianjin-Tangshan Region

1Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China
2School of Earth and Space Sciences, Peking University, Beijing 100871, China

Received 13 December 2010; Revised 22 March 2011; Accepted 20 May 2011

Academic Editor: Yu Zhang

Copyright © 2011 Xiangwei Yu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In this study a new tomographic method is applied to over 43,400 high-quality absolute direct P arrival times and 200,660 relative P arrival times to determine detailed 3D crustal velocity structures as well as the absolute and relative hypocenter parameters of 2809 seismic events under the Beijing-Tianjin-Tangshan region. The inferred velocity model of the upper crust correlates well with the surface geological and topographic features in the BTT region. In the North China Basin, the depression and uplift areas are imaged as slow and fast velocities, respectively. After relocation, the double-difference tomography method provides a sharp picture of the seismicity in the BTT region, which is concentrated along with the major faults. A broad low-velocity anomaly exists in Tangshan and surrounding area from 20 km down to 30 km depth. Our results suggest that the top boundary of low-velocity anomalies is at about 25.4 km depth. The event relocations inverted from double-difference tomography are clusted tightly along the Tangshan-Dacheng Fault and form three clusters on the vertical slice. The maximum focal depth after relocation is about 25 km depth in the Tangshan area.