1999年集集地震前后台湾地区地震b值及应力场时空演化特征  

Temporal and spatial evolution characteristics of b value and stress field in Taiwan before and after the 1999 Chi-Chi Earthquake

作　　者：高雅婧 孙云强 罗纲 GAO YaJing;SUN YunQiang;LUO Gang(Key Laboratory of Computational Geodynamics,Chinese Academy of Sciences,Beijing 100049,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;College of Transportation and Civil Engineering,Fujian Agriculture and Forestry University,Fuzhou 350002,China;School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,China;Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan University,Wuhan 430079,China)

机构地区：[1]中国科学院计算地球动力学重点实验室,北京100049 [2]中国科学院大学地球与行星科学学院,北京100049 [3]福建农林大学交通与土木工程学院,福州350002 [4]武汉大学测绘学院,武汉430079 [5]武汉大学地球空间环境与大地测量教育部重点实验室,武汉430079

出　　处：《地球物理学报》2022年第6期2137-2152,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41974107);中国地震科学实验场专项(2019CSES0112)资助。

摘　　要：地震b值时空分布及演化是地震孕育研究及地震危险性评价的重要指标.本文首先基于台湾地区1999年至2005年期间的地震目录数据,对该区进行地震b值时空扫描,得到了台湾地区的b值时空分布,分析了1999年M_(W)7.6台湾集集地震前后b值时空演化特征;进一步基于GPS速度场数据估算了地震前后区域的应变率和差应力率分布特征与变化;最后分析并探讨了b值分布、演化与差应力率场的关系.结果显示:(1)集集地震前后的1999—2005年,震中所在地震区的b值呈现出震前降低-震后先升高后降低的演化特征,反映区域应力的累积-释放-累积的过程;(2)集集地震震后的2003—2005年,由GPS速度场数据获得的震源区差应力率较大,意味着差应力累积速率较高,可能与震后中下地壳和上地幔黏弹性应力松弛有关,而相同时间段震源区的b值较高,意味着震源区附近上地壳差应力仍然较低,该时段震后过程仍在持续;(3)台湾西南和东部海岸山脉逆冲作用较强,差应力率较大,而b值较小,均可能意味着其背景差应力水平较高;台湾地区沿中央山脉由北至南存在扩张拉伸作用,差应力率较小,而b值较大,都意味着背景差应力水平可能较低.本文的结果对认知台湾地区地震活动变化、台湾地震孕育过程及地震b值与应力的关系具有重要作用.The temporal and spatial evolution of seismic b value is one of the important indexes for seismological research and seismic risk assessment.Based on the seismic catalogue from 1999 to 2005 in Taiwan,we first estimated the spatial and temporal distribution of b value in Taiwan,and analyzed the spatial-temporal evolution characteristics of b value before and after 1999 M_(W)7.6 Chi-Chi Earthquake.Furthermore,we estimated the strain rates and stress rates characteristics based on GPS velocity field in Taiwan.Finally,we analyzed and discussed the relationship between b value distribution,evolution and differential stress rates.The results show that:(1)From 1999 to 2005,before and after Chi-Chi Earthquake,b value of the earthquake zone presents the evolution characteristics of decreasing before earthquakes,increasing after earthquakes,and then decreasing,reflecting the process of accumulation-release-accumulation of regional stress.(2)In the period from 2003 to 2005,after the earthquake,the differential stress rates obtained by GPS velocity data in epicenter area are larger,which means that the accumulative rates of differential stress are higher,which may be related to the viscoelastic relaxation of lower middle crust and upper mantle after the earthquake.However,the b values in epicenter area are higher,which means that the differential stress level is lower,and the post-seismic process is still continuing.(3)The thrust of southwest and eastern Coastal Range of Taiwan is strong,the differential stress rates are larger,b values are smaller,which mean that the background differential stress level may also be larger.However,the dilation and stretching occur from north along Central Range to south of Taiwan,the differential stress rates are smaller,b values are larger,which mean that the background differential stress level may also be smaller.These results are of significance for understanding seismicity variation,seismogenic process in Taiwan Region,and the relationship between b value and stress.

关 键 词：震级-频度关系 B值 台湾地区 集集地震 应力率 应变率 

分 类 号：P315[天文地球—地震学]