2022年1月8日青海门源6.9级地震的震源区结构特征和b值意义初探  

Seismic structure and b-value in the focal area of the 8th January 2022 Menyuan,Qinghai M_(S)6.9 earthquake

作　　者：孙安辉[1] 高原[1] 赵国峰[2,3] 任超 梁姗姗 SUN AnHui;GAO Yuan;ZHAO GuoFeng;REN Chao;LIANG ShanShan(Key Laboratory of Earthquake Prediction,Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;China Earthquake Networks Center,Beijing 100045,China;National Earthquake Data Center,Beijing 100045,China)

机构地区：[1]中国地震局地震预测研究所(地震预测重点实验室),北京100036 [2]中国地震台网中心,北京100045 [3]国家地震科学数据中心,北京100045

出　　处：《地球物理学报》2022年第3期1175-1183,共9页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41974050,4180040231);国家重点研发计划(2017YFC1500304)资助。

摘　　要：2022年1月8日1时45分青海省门源县发生M_(S)6.9地震.本文基于青藏高原东北缘水平分辨率为0.3°的地震层析成像结果,获取了震源周边区域的地壳浅部构造信息,包括波速、泊松比以及估计的裂隙密度和饱和率的空间分布.结果表明:此次门源M_(S)6.9地震发生在P波和S波波速剧烈变化的区域,靠近高速体的边缘.泊松比和饱和率同样都显示,门源M_(S)6.9地震发生在高低值变化的过渡区.地震活动参数分析显示,震前冷龙岭断裂带的震源周边区域显示出了低b值、较低的a值和高a/b值的特征,与龙门山—岷山构造带强震之前的情况类似.裂隙密度在冷龙岭断裂两侧呈现出显著差异,北侧高于南侧,这可能是震后现场科考发现的断裂带地表破裂北侧高于南侧的构造成因.On 8^(th) January 2022,the M_(S)6.9 earthquake occurred in Menyuan County,Qinghai Province,China.Basing on the tomographic results of the NE Tibetan Plateau with a horizontal resolution of 0.3°,we present tomographic images of the middle-upper crust around the focal area,including seismic velocity(V_(P) and V_(S))and Poisson′s ratio(σ),and estimate structures of crack density(ε)and saturation rate(ξ)using the obtained V_(P),V_(S) andσvalues.Our results reveal that the Menyuan M_(S)6.9 earthquake is located close to the edge parts of the high velocity zones where V_(P) and V_(S) change abruptly,as well as the patterns ofσandξindicating.Distributions of seismic parameters(a,b,a/b)of the Lenglongling fault zones around the focal area share similar characters to those along the Longmenshan-Minshan fault zones with low-b,low-a and high-a/b values before the strong earthquakes.Crack density(ε)on the north of the Lenglongling fault is much higher than that on the south in the shallow crust,which may cause larger surface ruptures on the north of the Lenglongling fault by field survey after the earthquakes.

关 键 词：门源M_(S)6.9地震 地震层析成像 波速 泊松比 裂隙密度 饱和率 B值 

分 类 号：P315[天文地球—地震学]