滇中地区区域应力场研究

Research on regional stress field in Central Yunnan province

选取了滇中地区13个云南区域数字地震台站的地震记录,截取了3.0级以上地震事件原始波形数据175个,读取了424条清晰的P波初动.采用格点尝试法求解该区域的综合震源机制解,得到研究区的应力场.结果表明:该区域P轴方位为334",倾角为1",T轴方位为244",倾角为3",说明该区主压应力优势方向为北北西—南南东向,张应力优势方向为北东东—南西西向.由综合震源机制解中两个节面解参数可知断层破裂面倾角大,说明在滇中地区川滇菱形块体内部及周边区域的地震以水平走滑错动为主.笔者还收集计算了1985—2012年33次中小震震源机制解,采用网格搜索法计算了该区构造应力场.通过对比分析发现2种方法得到的应力状态吻合程度好,与前人的研究一致,因此可信度高.此结果可用于分析该地区的地震地质背景和构造结构,为地球动力学环境的研究提供依据.

Seismic records of 13 Yunnan regional digital seismic stations in Central Yunnan were selected and 175 original waveform data of magnitude 3.0 earthquake events were intercepted.A total of 424 clear P wave initials were taken.The lattice point method was used to solve comprehensive focal mechanism solutions in this area,and the stress field in the study area was obtained.The results showed that the direction of P-axis was 334°,the angle of inclination was 1°,the direction of the study area of stress field T-axis was 244°,and the angle of dip was 3°,indicating that the predominant direction of main compressive stress in this area was north-north-westsouth-south-east and the dominant direction of stress is north-east-east-south-east-west.According to the solution parameters of the two sections in the comprehensive focal mechanism solution,it was known that the fault rupture face has a large dip angle,indicating that the earthquakes in the central and peripheral regions of Sichuan-Yunnan blocks in Central Yunnan were dominated by horizontal slippage.We also collected and calculated 33 focal mechanism solutions for small and medium-sized earthquakes from 1985 to 2012,and calculated the tectonic stress field using the grid search method.The comparative analysis showed that the stress states obtained by the two methods were in good agreement with the previous studies,so the reliability was high.This result can be used to analyze the seismic geological background and tectonic structure in this area and provide the basis for the study of geodynamic environment.