西南地区1900—1970年历史地震震源参数推断及结果的不确定性分析

西南地区处于青藏高原东缘川滇、巴颜喀拉和华南三大活动块体的交接部位,是我国地震活动最强烈的地区之一.然而该区大多数历史地震震源参数均存在缺失或者不准确的问题.本文主要通过以下三点工作:(1)基于西南地区地震地质及区域构造应力场研究结果,推断了西南地区M≥6.0的部分历史地震(1900年至1970年)断层面参数,并对结果的不确定性进行了分析,发现该推断断层面参数的方法在西南地区复杂的构造应力场条件下的适用程度有限;(2)使用1900年至1970年之间Shide Circulars (British Association for the Advancement of Science, Seismological Committee (BAASSC), 1900—1912),《国际地震资料汇编》(ISS)和EHB Bulletin的P波和S波到时,对该时间范围内41个地震事件重新定位,得到了其中32个地震事件的可靠定位结果;(3)使用1933年(ISS从1933年开始收录P波初动记录)至1970年之间ISS的P波初动,对该时间范围内的29个地震事件求解震源机制解,得到了其中14个地震事件的震源机制解的可靠结果,从而丰富了西南地区1900年来历史强震目录震源参数资料.

Inference of source parameters of historical major earthquakes from 1900 to 1970 in southwestern China and analysis of their uncertainties

Southwestern China, located in the conjoined areas of the Chuandian, Bayankala and Huanan active blocks on the eastern margin of the Qinghai-Tibetan Plateau, is one of the regions with highest seismicity in China. The source parameters of historical major earthquakes in this region are missing or inaccurate. This work focuses on the following three aspects. (1) Based on the geological data and tectonic stress field, we infer focal mechanisms of historical major earthquakes (M≥6.0) from 1900 to 1970 in southwestern China, and analyze uncertainties of the results to conclude that this indirectly method might not be applicable in all areas of southwestern China. (2) We relocate 41 events by using the Shide Circulars, International Seismological Summary and EHB Bulletin instrumental records within the time span and obtain 32 reliable results. (3) We calculate the focal mechanisms of 29 events by first motion records of P waveforms of ISS and obtain 14 reliable results. Consequently we enrich source parameter information of historical major earthquakes in southwestern China from 1900 to 1970.