樊文杰,崔效锋,赵小艳. 2022. 滇西北地区现今构造应力状态及其与地震的关系. 地震学报,44(4):632−643. doi: 10.11939/jass.20210036
引用本文: 樊文杰,崔效锋,赵小艳. 2022. 滇西北地区现今构造应力状态及其与地震的关系. 地震学报,44(4):632−643. doi: 10.11939/jass.20210036
Fan W J,Cui X F,Zhao X Y. 2022. Current state of tectonic stress in northwestern Yunnan and its relationship with earthquakes. Acta Seismologica Sinica44(4):632−643. doi: 10.11939/jass.20210036
Citation: Fan W J,Cui X F,Zhao X Y. 2022. Current state of tectonic stress in northwestern Yunnan and its relationship with earthquakes. Acta Seismologica Sinica44(4):632−643. doi: 10.11939/jass.20210036

滇西北地区现今构造应力状态及其与地震的关系

Current state of tectonic stress in northwestern Yunnan and its relationship with earthquakes

  • 摘要: 基于搜集到的2000—2018年滇西北地区MS≥3.0地震的震源机制解,运用线性叠加反演法进行应力场反演,分析了滇西北地区现今的构造应力状态,进一步探讨了应力张量方差的时空分布与地震活动的关系。结果显示:① 滇西北地区地震的震源机制解类型复杂,主要以走滑型(46%)为主,正断型(27%)次之;② 研究区的构造应力场具有整体的一致性和局部的非均匀性,呈现为NNW向挤压和ENE向拉张的走滑型应力结构,说明研究区受到来自NNW向的水平挤压作用,对该地区上地壳运动和断裂活动起主导作用;③ 滇西北地区的应力张量方差大都小于0.2,除北部一些地区外,应力场基本处于均匀状态。根据应力张量方差随时间的变化和后续地震可知,中强地震大都发生在应力张量方差值低于0.2的情形,且主要发生在应力张量方差减小即震源机制解趋于一致的过程中。空间上这些地震基本都发生在应力张量方差的低值分布区及其边缘,这一结果有助于判定发震地点和了解区域应力集中增强过程。

     

    Abstract: Based on collected the focal mechanism solutions of MS≥3.0 earthquakes from 2000 to 2018 in northwestern Yunnan, we analyze the current state of tectonic stress in northwestern Yunnan by Michael’s linear superposition stress inversion method, and further investigate the spatio-temporal distribution of stress tensor variance and its relationship with seismic activity. The results show that the focal mechanism solutions of earthquakes in northwestern Yunnan are complex in types, mainly strike-slip type (46%), followed by normal-faulting type (27%). Tectonic stress field is overall consistency and partial inhomogeneity. The tectonic stress field shows strike-slip faulting stress regime with NNSwards principal compressive stress and ENEwards principal tensile stress in the studied area. It suggests that the study area is subjected to horizontal compression from NNW direction, which plays a dominant role in the upper crustal movement and fault activities in this area. Regional grid stress inversion shows that the variance is mostly below 0.2 in northwestern Yunnan, which indicates that the stress field is in a uniform state except for some northern regions. According to the variation of variance with time and subsequent earthquakes, moderate to strong earthquakes in the studied area mostly occurred when the stress tensor variance was lower than 0.2. Most earthquakes mainly occurred during the process that the stress tensor variance decreased, that is, when the focal mechanism solutions tend to be consistent. And spatially these earthquakes basically occur in the low value zones of the variance or near the edge of the zones, which provides reference for judging the earthquake location and comprehending the regional stress concentration enhancement process in the future.

     

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