Types of focal mechanism solutions and parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces |
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| Authors: | CHENG Wan-zheng RUAN Xiang ZHANG Yong-jiu |
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| Institution: | 1. Earthquake Prediction Institute, Earthquake Administration of Sichuan Province, Chengdu 610041, China
2. Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China |
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| Abstract: | Based on P-and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928
M≥2.5 earthquakes (1994–2005) in four sub-blocks of Sichuan and Yunnan Provinces, namely Sichuan-Qinghai, Yajiang, Central
Sichuan and Central Yunnan blocks. Combining these calculation results with those of the focal mechanism solutions of moderately
strong earthquakes, we analyzed the stress field characteristics and dislocation types of seismogenic faults that are distributed
in the four sub-blocks. The orientation of principal compressive stress for each block is: EW in Sichuan-Qinghai, ESE or SE
in Yajiang, Central Sichuan and Central Yunnan blocks. Based on a great deal of focal mechanism data, we designed a program
and calculated the directions of the principal stress tensors, σ1, σ2 and σ3, for the four blocks. Meanwhile, we estimated the difference (also referred to as consistency parameter
) between the force axis direction of focal mechanism solution and the direction of the mean stress tensor of each block.
Then we further analyzed the variation of
versus time and the dislocation types of seismogenic faults. Through determination of focal mechanism solutions for each block,
we present information on the variation in
value and dislocation types of seismogenic faults.
Foundation item: National Key Basic Research Development and Programming Project (2004CB418404) and Joint Seismological Science
Foundation (105004). |
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| Keywords: | focal mechanism solution dynamic stress field dislocation type of earthquake source consistency parameter Sichuan-Yunnan block |
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