汶川、 芦山地震前后四川地区应力场时空演化

摘要/Abstract

摘要： 基于四川地区2000年1月~2014年6月M_L≥3.0地震震源机制解, 首先分析了四川地区各次级地块和不同断裂带的地震震源机制类型及整体应力场特征, 其次以汶川8.0级、芦山7.0级地震为例, 研究两次强震发生前后四川各次级地块的主压应力时空演化特征。获得的主要认识为: ① 四川各次级地块的地震震源机制比较紊乱, 反映了块体内部构造的复杂性, 而断裂带的地震震源机制则相对比较单一, 与其运动类型一致; ② 四川各次级地块及断裂带的整体应力方向比较一致, 优势方位呈现NW和NWW向, 倾角接近水平; ③ 汶川8.0级、芦山7.0级地震发生前, 震中所在的龙门山断裂带中南段及川青地块的主压应力方位均出现过较好的一致性, 而在芦山地震后, 龙门山断裂带及川青、川中地块的主压应力优势方位则转变为NE向。

关键词: 区域应力场, 次级地块, 震源机制解, 阻尼反演, 汶川地震, 芦山地震

Abstract: Based on the focal mechanism solutions of M_L≥3.0 earthquakes from January 2000 to June 2014 in Sichuan area, the focal mechanism type and stress field of every sub-blocks and different fault zones are analyzed. Take the 2008 Wenchuan 8.0 and the 2013 Lushan 7.0 earthquake for example, we study spatial-temporal evolution characteristic of main compressive stress in the sub-blocks of Sichuan before and after the two strong shocks. The major results are: (1) the focal mechanism types in the sub-blocks of Sichuan are relatively in disorder, which may reflect the complexity of internal structure in blocks, and that focal mechanism solutions of earthquakes along fault zones are relatively in singleness, which are consistent with the dislocation type of fault. (2) The stress direction of the sub-blocks and fault zones in Sichuan shows good consistency, the dominant orientations presents in NW and NNW, and the dip angle is close to horizontal. (3) before the Wenchuan 8.0 and Lushan 7.0 earthquake, the main pressure stress orientation of Sichuan—Qinghai block and middle-south sections in Longmenshan fault zone all appear good consistency,which is in NW direction, and after the Lushan 7.0 earthquake, the main pressure stress orientation in Sichuan—Qinghai, Central Sichuan blocks and the Longmenshan fault zone turn into NE direction.

Key words: Regional stress field, Focal mechanism solution, The Sub-block of Sichuan area

中图分类号:

P315.7

张致伟, 阮祥, 王晓山, 王宇航, 祁玉萍. 汶川、芦山地震前后四川地区应力场时空演化[J]. 地震, 2015, 35(4): 136-146.

ZHANG Zhi-wei, RUAN Xiang, WANG Xiao-shan, WANG Yu-hang, QI Yu-ping. Spatial-temporal Evolution of Stress Fields in Sichuan Area before and after the 2008 Wenchuan and the 2013 Lushan Earthquake[J]. EARTHQUAKE, 2015, 35(4): 136-146.

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