川滇块体及周边区域现今震源机制和应力场特征

doi:10.3969/j.issn.0253-4967.2014.02.011

摘要/Abstract

摘要： 利用CAP（Cut and paste）方法获取了川滇块体及周边区域2007年8月至2013年4月75次3.5级以上中等地震的震源机制解，结合哈佛大学历史地震震源机制解，分析了震源机制解和震源深度的空间分布特征，并探讨了其构造动力学背景。结果表明：1）川滇块体各不同断裂带、块体内部各次级块体之间、块体内外表现出不同的震源机制解空间分布特征，揭示出位于青藏高原东南缘的川滇块体及周边地区应力场的非均匀性；2）研究区各主要断裂带所反映的与构造背景作用一致的震源机制分布特征表明，川滇块体及周边近期断层破裂方式主要受到各个断裂带的构造活动以及次级块体之间相互作用的控制；3）丽江-小金河断裂带上特殊的震源机制特征和发震应力轴的分布特征，进一步证实了丽江-小金河断裂带对高原逃逸物质的抵挡和屏蔽的作用；4）震源深度分布特征表明，川滇块体及周边地震震源深度主要分布于15km的上地壳，优势分布在5～15km的范围，揭示出研究区的地壳脆性孕震层位于5～15km的上地壳。

关键词: 川滇块体, 震源机制解, CAP方法, 应力场, 震源深度

Abstract: Because of the special geographical location and complex tectonic background of the Chuan-Dian rhombic block and its adjacent areas, researches on the tectonic stress and fault mechanics of the region have been a concern for scientists, recently. Focal mechanism solutions and focal depths of 75 M≥3.5 moderate earthquakes occurring in the Chuan-Dian rhombic block and its adjacent regions from Aug. 1st, 2007 to Apr.21th, 2013 are obtained by using CAP method. Combining the results with the historical focal mechanism solutions from Harvard CMT, the characteristics of the spatial distribution of the focal mechanisms and focal depths are investigated, and their tectonodynamic background is discussed. Main conclusions are drawn as follows. 1)The spatial distributions of focal mechanisms differ among different faults and sub-blocks inside the block and those outside the block, which indicate the heterogeneity of the regional stress filed. 2)Spatial distribution of focal mechanisms is consistent with the tectonic background, suggesting that the recent faulting and earthquake mechanisms of the Chuan-Dian rhombic block and its adjacent regions are controlled mainly by the faulting of respective fault zones and the interaction between sub-blocks. 3)The special features of focal mechanisms, P axis and T axis distribution in the Lijiang-Xiaojinhe Fault zone further confirm the absorption and shielding effect of the fault on the plateau's escaping masses. 4)The predominant focal depth in the Chuan-Dian rhombic block and its adjacent region is 5 to 15km, suggesting that brittle seismic layer beneath the Chuan-Dian rhombic block is in the upper crust.

Key words: Chuan-Dian rhombic block, focal mechanism, CAP method, stress field, focal depth

中图分类号:

P315.3⁺3

罗钧, 赵翠萍, 周连庆. 川滇块体及周边区域现今震源机制和应力场特征[J]. 地震地质, 2014, 36(2): 405-421.

LUO Jun, ZHAO Cui-ping, ZHOU Lian-qing. CHARACTERISTICS OF FOCAL MECHANISMS AND STRESS FIELD OF THE CHUAN-DIAN RHOMBIC BLOCK AND ITS ADJACENT REGIONS[J]. SEISMOLOGY AND GEOLOGY, 2014, 36(2): 405-421.

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