Seismological Study on Behaviors of Present-Day Movement of Arcuate Tectonic Belt in Southeast Yunnan
详细信息
- 责任者：Hu Nan (Key Laboratory of Active Tectonics and Volcano ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Han Zhujun
- 刊名：Seismology and Geology
- 出版年：2013
- 卷期：35(1)
- 关键词：弧形构造 ; arcuate structure ; 地震活动性 ; seismicity ; 云南 ; Yunnan Province
- 页码：p.1-21
- 图表：illus., 72 refs.
- 分类号：0500
- issnNo：ISSN0253-4967
- isbnNo：CN11-2192/P
摘要
The accurate relocations of small earthquakes during 1990-2011 on the arcuate tectonic belt in southeast Yunnan(23°N to 25°N,101°E to 103°E)are obtained by hypo2000 and double difference algorithm using Pg and Sg phase readings of 721 earthquakes recorded by Yunnan Earthquake Network Center.The RMS residual decreases to 0.45 from 1.43 with an average precision of about 1.4km horizontally and 1.9km vertically after relocation. Then we collected the waveform data of the study region during 2007-2012 and calculated the focal mechanisms of 148 small earthquakes with the method of the maximum amplitude ratio between Pg and Sg. Focal mechanism result shows that the number of nodal planes representing normal strike-slip is almost twice of that of the reverse strike-slip,which demonstrates that the dominant movement on the arcuate tectonic belt is normal strike-slip currently. Relocation of small earthquakes greatly improves the definition of the seismic images on the faults that generate them. According to the relocated focal depths,the Qujing Fault and Shiping-Jianshui Fault dip southwest,and the Honghe Fault dips northeast,which are in accord with the fault geometric characteristics revealed by crustal velocity profiles. According to this,the rollback of Sumatra-Myanmar trench has already brought a deep effect on the arcuate tectonics in southeast Yunnan,the compression caused by the slip of Sichuan-Yunnan rhombic block towards SSE may be weakened. So the tensile stress in SWW-NEE direction plays a more important role in present-day activities of the arcuate tectonics compared to the compressive stress in SSE-NNW direction,which can also be deduced from the characteristics of focal mechanism parameters. A transtensional zone may be emerging from the arcuate tectonics in southeast Yunnan.