【作者】 张晓阳； 邓津； 李淑婷；

【Author】 ZHANG Xiao-Yang;DENG Jin;LI Shu-Ting;Nation Field scientific Observation and Research Station of Geophysics in Lanzhou,Gansa Province;Key Laboratory of Loess Earthquake Engineering,China Earthquake Administration,Gansu province;Lanzhou institute of Geotechnical seismology,China Earthquake Administration;

【机构】 甘肃兰州地球物理国家野外科学观测研究站； 中国地震局(甘肃省)黄土地震工程重点实验室； 中国地震局兰州岩土地震研究所；

【摘要】 利用2009年以来国家地震科学数据中心编目的地震目录资料,以2019年甘肃夏河Ms5.7级地震为研究对象,利用EMR方法对研究区域的最小完整性震级M_c进行了分析,采用最大似然法进行b值空间扫描,获取到夏河地震前后的b值变化,分析了地震前后的应力演化过程。研究结果显示:(1)最小完整性震级为M_c=0.7,从时间尺度来看,M_c自2009年始逐步降低,研究区域的地震监测能力在逐步提高,夏河地震前Mc开始升高之后又缓慢恢复,可能是由于在中强地震发生后小震级余震的缺失导致的;(2)夏河地震前存在显著低b值区域,低b值区域特征为震源区域b值无明显变化,震源周边区域出现较明显低b值异常,该异常特征反映了地震孕育的应力积累过程,对地震孕育过程和地震预测研究有重要意义;(3)从夏河地震与低b值空间分布关系来看,夏河地震的发生未充分释放该地区应力,该地区的中强地震危险性仍然存在。更多还原

【Abstract】 Based on the catalog data compiled by the National Earthquake Science Data Center since 2009,taking the Xiahe Ms5.7 earthquake in Gansu Province in 2019 as the research object,the minimum magnitude of completeness in the study area was analyzed by EMR method.The maximum likelihood method was used to scan the b-value space,and the b-value changes before and after the Xiahe earthquake were obtained.The stress evolution process before and after the earthquake was analyzed.The results show that:(1) The minimum magnitude of completeness is Mc=0.7.From the time scale, Mc has gradually decreased since2009,and the seismic monitoring ability of the study area has gradually improved.Before the Xiahe earthquake,Mc began to rise and then recovered slowly,which may be due to the lack of small earthquakes after the occurrence of moderate earthquakes.(2) There is an obvious low b value area before the Xiahe earthquake.The low b value area is characterized by no obvious change in the b-value of the source area,and the obvious low b-value anomaly appears in the surrounding area of the source.The abnormal characteristics reflect the stress accumulation process of earthquake preparation,which is of great significance to the study of earthquake preparation process and earthquake prediction.(3) From the spatial distribution relationship between Xiahe earthquake and low b-value,the occurrence of Xiahe earthquake did not fully release the stress in the region,and the medium-strong earthquake risk in the region still existed.更多还原