摘要
2007年6月3日在云南宁洱发生6.4级地震,震后云南省地震局在主震附近架设了5套流动数字地震台。利用这些地震台和思茅固定地震台记录的震相数据,采用双差定位法对宁洱6.4级地震的余震序列重新进行精定位。结果显示,宁洱地震序列的长度约为40km,宽度约为10km,明显集中在普洱断裂与NNE向断裂横断错移的构造部位,且大部分余震发生在主震附近的普洱断裂。余震序列的优势分布方向明显,震源深度分布从浅层2km至12km,大多数集中在8～10km优势分布范围内,平均深度为7.9km,并且平行于地震序列剖面显示的地震破裂活动沿NW向倾斜,与NE向孟连-墨江断裂带在震区的次级断层倾向一致。地震在密集区的NW段比SE段要多,可能与当地的地下介质或断裂有关。垂直于地震序列剖面显示定位后地震主要密集分布在普洱断裂附近,地震序列的破裂活动沿SW方向倾斜,与普洱西支断裂倾向一致。总之,精定位后的断层走向和震源机制解的走向吻合得非常好,主震位于余震序列上端,余震在主震下端较为对称地分布,说明断层朝SE方向和NW方向破裂比较充分。
Five mobile digital seismic stations were set up by Earthquake Administration of Yunnan near the epicenter of the main shock after the Ning＇er M6.4 earthquake on June 3,2007.In this paper,the aftershock sequence of the Ning＇er M6.4 earthquake is relocated by using the double difference earthquake location method.The data are from the 5mobile digital seismic stations and the permanent Simao seismic station.The result shows that the length of aftershock sequence is 40km and the width is 30km,concentrated obviously at the lateral displacement area between the Pu＇er fault and the NNE-trending faults,with the majority occurring on the Pu＇er fault around the main shock.The depths of aftershocks are from 2km to 12km,and the predominant distribution is in the depth of 8～10km.The mean depth is 7.9km.The seismic fault dips to the northwest revealed from the profile parallel to this aftershock sequence,which is identical to the dip of the secondary fault of the NE-trending Menglian-Mojiang Fault in the earthquake area.There are more earthquakes concentrated in the northwest segment than in the southeast segment,which is perhaps related to the underground medium and faults.The depth profile of the earthquake sequence shows that the relocated earthquakes are mainly located near the Pu＇er fault and the seismic ruptures dip to the southwest,consistent with the dip of the west branch of the Pu＇er fault.In all,the fault strike showed by earthquake relocations matches well with the strike in the focal mechanism solutions.The main shock is in the top of the aftershock sequence and the aftershocks are symmetrically distributed,which shows that the faulting was complete in both NE and SW directions.
出处
《地震地质》
EI
CSCD
北大核心
2011年第3期560-567,共8页
Seismology and Geology
基金
地震科学联合基金(200804)资助
关键词
宁洱6.4级地震
流动数字地震台网
双差地震定位法
the MS 6.4 Ning＇er earthquake
mobile digital seismic station
double-difference earthquake location algorithm
