云南及邻区应力应变场分区耦合特性初步研究

COUPLING CHARACTERISTICS OF STRESS AND STRAIN AT DIFFERENT LAYERS OF DIFFERENT SUB-REGIONS IN YUNNAN AND ITS ADJACENT AREAS

利用云南及邻区遥测台网记录到的6361条近震数据,采用互相关系数法计算16个台站共64条S波分裂事件,同时收集了8个序列的S波分裂研究结果,初步给出了云南及邻区横波分裂的分布特征;应用哈佛大学给出的43个中强震震源机制解,利用其P轴方位角平均结果,给出了云南及邻区3个主要分区地壳应力场的最大主压应力方位;根据“中国地壳运动观测网络”基本网1999—2004年的观测资料,按观测点给出了云南及邻区的主应变率分布;此外,还搜集到云南及邻区的SKS分裂结果和Pn波各向异性资料.通过研究发现:①作为强震孕育主体环境的大陆岩石圈在横向上具有明显的分块特点;②大陆岩石圈的力学行为随深度而变化,具有明显的分层特性;③云南及邻区所含的各活动地块可能具有不同类型,GPS所反映的地壳变形信息可能受到块体类型控制;④云南及邻区的地壳S波分裂可能受其上地壳甚至地表构造影响较大.

In this paper, we collect 6 361 waveform data to calculate the shear wave splitting parameters from a regional seismic network of 22 digital stations in Yunnan and its adjacent area from July 1999 to June 2005. By using the cross-correlation method, 64 splitting events of 16 stations are processed. We also collect the splitting results of 8 earthquake sequences to present the characteristics of shear wave splitting in Yunnan and its adjacent areas. The orientations of maximum principal compressive stress of 3 sub-regions in this area are derived from the CMT focal mechanism solutions of 43 moderate-strong earthquakes provided by Harvard University by the P axis azimuth-averaging method. The principal strain rate at each observatory is deduced from the observations of Crustal Move- ment Observation Network of China during the period from 1999 to 2004. In addition, the data of Pn anisotropy and SKS splitting of Yunnan and its adjacent areas are also collected. We have discovered from this study that the continental lithosphere, as a main seismogenic environment for strong earthquake, can be divided into blocks laterally; the mechanical behavior of lithosphere varies with depth and can be divided into different layers in the vertical orientation; the information of crustal deformation obtained from GPS might be affected by the type of blocks, since there are different types of active blocks in Yunnan and its adjacent areas; the shear wave splitting in this region might be affected mainly by the upper crust or even the surface tectonics.