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2014年2月12日于田7.3级地震序列震源机制特征分析
李金,王琼
新疆维吾尔自治区地震局,乌鲁木齐市新市区科学二街338 号830011
摘要:
基于新疆及西藏区域数字地震台网的宽频带资料,采用CAP 方法反演了2014 年2月12 日于田7. 3 级地震的前震、主震及早期MS≥3. 5 余震序列的震源机制解。结果显示,此次7. 3 级强震为带有正断分量的走滑型地震,结合震源区的构造和余震分布,节面I 走向241° /倾角90° /滑动角- 22°,判定该节面代表了主震的发震断层面。主震主压力轴方位为194°,与该区历史中强震主压应力P 轴方位近NS 向较为接近。其5. 4 级前震和主震震源机制解具有较高的一致性。18 次余震中有10 次为走滑型地震,其中6 次为正断型,2 次为逆断型,且70% 的地震的P 轴方位近SN 向。此次7. 3 级地震序列震源深度为5 ~ 28km,而大部分地震为15 ~ 20km,略大于本文得到的主震震源深度10km。
关键词:  于田7.3级地震  震源机制  CAP方法  余震
DOI:
分类号:
基金项目:新疆地震局基金(201401)和2014 年度震情跟踪合同制定向工作任务(2014020106)联合资助
The analysis on the characteristics of the focal mechanisms for the MS7. 3 earthquake sequence on February 12,2014 in Yutian
Li Jin Wang Qiong
Earthquake Administration of Xinjiang Uygur Autonomous Region,Urumqi 830011,China
Abstract:
Based on the broadband waveforms recorded by the Xinjiang and Tibetan Digital Seismic Networks,we inversed the focal mechanism solutions of the main shock,foreshock and MS≥3. 5 aftershocks of the MS7. 3 earthquake,by using the CAP method. The results showed that the focal mechanism of the main shock had Nodal plane I with strike 241° / dip 90° / rake - 22°,and Nodal plane II with strike 331° / dip 68° / rake - 180°,and the focal depth was about 10km. Combined with the active geologic structures of the seismic area,Nodal plane I was identified to be the seismogenic fault plane of the main shock. The direction of P-axis for the main shock was 194°,closed to the NS direction of P-axis of history earthquakes this area. The MS5. 4 foreshock,main shock and 10 aftershocks were strike-slip earthquakes. 6 aftershocks were normal faulting and 2 aftershocks were thrust type earthquakes. 70% of earthquake in the sequence had near NS direction P-axis. The focal depth of this MS7. 3 earthquake sequence distributed 5 ~ 28km,most of the earthquakes occurred within the depth range of 15 ~ 20km,slightly deeper than the focal depth 10km we calculated.
Key words:  Yutian MS7.3 earthquake  Focal mechanism  CAP method  Aftershock