重庆地区地震震源机制解及动力环境分析
投稿时间:2018-04-17  修订日期:2018-06-23  点此下载全文
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冯梅 中国地质科学院 mei_feng_cn@163.com 
基金项目:本文由中国地质局地质调查项目(DD20160268)和国家自然科学基金面上项目(41574049)联合资助
中文摘要:使用中国地震台网约100台原始观测波形数据,利用FOCMEC震相法确定了2017年11月23日5.0级重庆武隆和2016年12月27日4.9级重庆荣昌地震的震源机制解。同时搜集整理了重庆地区近年来其它震源机制资料。结果显示武隆地震属于走滑正断型,与2013年发生在七曜山断裂带中段的石柱地震活动性质相似,据此推断七曜山断裂以正断活动为主。发生在华蓥山断裂带南段的荣昌地震属于走滑逆冲型,推断华蓥山断裂(南段)以逆冲活动为主。从区域震源机制解结果来看,华蓥山断裂南段所在的重庆西部主要受近东西向挤压构造应力控制,与华南区域构造应力场基本一致。七曜山断裂带所在的重庆中、东部主要受近南北向挤压应力控制,与现今华南区域构造应力场不一致。据此推断,重庆中、东部处于一个与周围应力和构造活动方式都不同的独特环境。重庆中、东部至两湖平原地区处于特提斯构造域和环太平洋构造域的转换过渡区,其独特的现今应力环境似乎该区现今不受两大构造域的影响。
中文关键词:震源机制解  应力  七曜山断裂  华蓥山断裂  重庆
 
Focal mechanisms of earthquakes in Chongqing and geodynamical implications
Abstract:Using waveforms recorded by about one hundred seismic stations of the China Seismic Network and the phase-based method of FOCMEC, we determined focal mechanisms for the Ms 5.0 earthquake occurred on November 23, 2017, in Wulong and the Ms 4.9 earthquake on December 27, 2016, in Rongchang. We also collected focal mechanisms for other earthquakes recently occurred in Chongqing. Our results show that the Wulong earthquake on southern Qiyaoshan fault is an oblique normal fault activity, similar to another earthquake recently occurred in Shizhu on central Qiyaoshan fault. We therefore infer that the Qiyaoshan fault is characterized by normal activities. The Rongchang earthquake on southern Huayingshan fault is a reverse fault activity with strike-slip component, similar to other earthquakes in the region. So, the (southern) Huayingshan fault is characterized by reverse activities. On a regional view of focal mechanism results, the western part of Chongqing where the Huayingshan fault is located is mainly controlled by tectonic stress in rough E-W direction, which is similar to the stress environment in the South China. The central and eastern part of Chongqing where the Qiyaoshan fault is located is mainly controlled by tectonic stress in rough S-N direction, which is similar to the stress environment in the area from Chongqing to Hubei-Hunan plain. However, the stress field is different with background (rough E-W) stress environment in South China. All those indicate that the areas from the central and eastern part of Chongqing to Hubei-Hunan plain are in a special dynamic environment. In fact, the areas are in the transition region between two global tectonic domains, Tethyan and circum-Pacific tectonic domains. The distinctive present stresses imply that the region from central and eastern Chongqing to Hubei-Hunan plain seems not to be affected by the two global tectonic domains in the present.
keywords:Focal Mechanism  Stress  Qiyaoshan Fault  Huayingshan fault  Chongqing
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