全国主要构造区近期应变积累动态演化研究

Research on Dynamic Evolution of Strain Accumulation inMain Tectonic Areas of China

摘要:

利用2004-2007、2009-2011、2009-2012年全国GPS水平运动速度场资料，借助负位错反演，分析相关构造断裂应变积累动态演化特征，寻找目前强震孕育背景相对显著的构造断裂区段，并探讨芦山地震前异常状况及汶川、日本等大震后应变积累的可能变化。结果表明：①日本巨震后华北构造区、汶川—玉树大震后川滇地区近1至数年主要构造断裂中应变积累减缓的略占多数；甘肃东南部的西秦岭构造区应变积累在汶川震后的一段时间速率加快；汶川震后龙门山断裂南段维持应变积累，2012年还略微增速，一定程度上反映出芦山震前背景信息。②目前强震甚至大震孕育背景相对显著的构造区域有南天山断裂西段及与西昆仑北缘断裂交汇区、安宁河断裂及与则木河断裂交汇区、红河断裂中段、祁连山断裂带西段、晋冀蒙交界区，及上述区域附近。

Abstract:

Xinjiang，the northeastern margin of Qinghai-Xizang block，Sichuan-Yunnan，and North China are main tectonic and seismic regions of China. Fortunately，these regions contain dense network of GPS stations that can be used to study strain accumulation.In this paper，strain accumulations in these regions of the Chinese mainland are studied over the time periods of 2004-2007，2009-2011，and 2009-2012. We use GPS data and horizontal velocity fields that are aided by inversion of negative dislocation.Dynamic evolution features of strain accumulation at related fractures are discussed，together with abnormal status before the Lushan earthquake，and possible variation of strain accumulation after the Wenchuan and Japan great earthquakes.The results indicate that：（1） For one to several years，in North China after the Japan MS9.0 huge earthquake and the Sichuan-Yunnan area after the Wenchuan-Yushu great earthquakes，the strain accumulation rate decreased for most tectonic faults，which suggests that there is a possibility of adjustment influence after great earthquakes.It the West Qinling tectonic region in the southeastern Gansu，for a certain period after the Wenchuan earthquake，the strain accumulation rate increased，possibly showing influence of the Wenchuan great earthquake to some degree，and corresponding with the occurrence of the Minxian-Zhangxian MS6.6 earthquake in July 2013.After the Wenchuan earthquake，the southern segment of Longmenshan fault continued to accumulate strain with a slight increase in strain accumulation rate observed in 2012.This may reflect background information of strong earthquake preparation before the Lushan great earthquake to some degree.（2） Higher energy accumulation background exists at the west segment of the Southern Tianshan fracture and in the region where it meets the Northern margin fault of Western Kunlun.This same phenomenon is observed where the Anninghe fault meets the Zemuhe fault，in the middle segment of Honghe fracture，in the western segment of Qilianshan fracture，and the boundary between Shanxi，Hebei，and Neimeng.