摘要
2014年10—12月期间,云南景谷接连发生了Ms6.6、Ms5.8、Ms5.9三次中-强地震。为确定地震的地质构造成因,在地表调查的基础上,综合该区的地质构造情况、烈度与余震分布、震源机制解等资料,确定此次震群活动的宏观震中位于永平盆地东南侧山地,发震断层为地质与地貌表现不显著的NW向右旋走滑断层。此次震群活动及余震迁移过程指示,由于断层斜接部位岩桥的临时阻碍,Ms6.6地震破裂在向南东扩展过程中发生短暂停滞,突破障碍后进一步引发了Ms5.8和Ms5.9地震,这符合震源破裂沿NW向发震断裂分段破裂的行为。区域活动断裂的遥感解译结果发现,发震断层位置恰好处于NW向右旋走滑的茶房断裂与普文断裂之间,区域上属于该断裂带的不连贯部位,指示此次中-强震群活动应该是茶房-普文断裂带贯通过程的构造活动表现。结合思茅地块的历史地震资料发现,思茅地块地震活动多以小于等于6.8级为主,发震构造多为NW向断裂。指示在现今构造应力场作用下,该区NW向断裂的活动性相对NE向断裂更加显著,属于该区主要控震构造,应在今后的地震地质工作中给予更多关注。
Yongping Town in Jinggu of Yunnan Province experienced three times of strong earthquakes from October to December in 2014, which were Ms6.6, Ms5.8, Ms5.9 respectively. In order to determine the cause of this earthquake swarm in the geological structure area, the authors, based on the investigation at the surface in combination with the geological structure, intensity and the af- tershock distribution and focal mechanism solution, have reached the conclusion that the macro epicenter of the earthquake swarm ac- tivity was located in the mountain area on the southeast side of Yongping basin. The seismogenic fault was the NW-trending dextral strike slip fault which had no obvious geological and geomorphological features. The southeastward migration phenomenon of the af- tershocks indicates, due to the temporary block of the oblique connecting position of the rock bridge fault, there was a brief stagna- tion when Ms6.6 earthquake rupture propagation was spread southeastward. Nevertheless, on December 6th, after breaking through barriers, the earthquake rupture further triggered the MsS.8 and MsS.9 earthquakes. This shows that the earthquake swarm activity ac- corded with the behavior of focal rupture along the ~ seismogenic fault segment rupture. The remote sensing interpretation of re- gional active faults indicates that the seismogenic fault lay just between Chafang NW-trending right strike-slip faults and Puwen IxFW-trending right strike-slip faults. The area belongs to the incoherent area of Chafang-Puwen fault zone. The authors point out that the strong earthquake swarm activities should be tectonic activities during the coalescence of Chafang-Puwen fault in the upper crust. Combined with the historical seismic data of the Simao block, it is held that the grades of all the seismic activities were less than or equal to 6.8, and the seismogenic structures were mostly N＇W-trending faults. These phenomena indicate that, in the present tec- tonic stress field, the NW-trending fault activity is more obvious relative to the NE-trending fault and belongs to the main earth- quake controlling structure, which deserves much attention in furture seismic geological work.
出处
《地质通报》
CAS
CSCD
北大核心
2016年第1期140-151,共12页
Geological Bulletin of China
基金
中国地质调查局项目(编号:1212011120163
12120114002101)
国家自然科学基金项目(批准号:41171009)
中国地质科学院地质力学研究所基本科研业务费项目(编号:DXLXJK201410)
关键词
震群活动
发震断层
控震构造
断层扩展
茶房-普文断裂带
earthquake swarm activity
seismogenic fault
earthquake-controlling structure
fault propagation
Chafang-Puwen fault zone
