沂沭断裂带及其邻区地壳P波层析成像研究  

Crustal P-wave tomographic study of the Yishu fault zone

作　　者：崔鑫[1,2] 宋秀青[3,4] 石耀霖 殷海涛 朱元清[3,4] 董腾超[1] CUI Xin;SONG Xiuqing;SHI Yaolin;YIN Haitao;ZHU Yuanqing;DONG Tengchao(Shandong Earthquake Agency,Jinan 250014,China;Institute of Geophisics,China Earthquake Administration,Beijing 100081,China;Shanghai Earthquake Agency,Shanghai 200062,China;Shanghai Sheshan Geophisical National Geophysical Obeservatory,Shanghai 201602,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]山东省地震局,山东济南250014 [2]中国地震局地球物理研究所,北京100081 [3]上海市地震局,上海200062 [4]上海佘山地球物理国家野外科学观测研究站,上海201602 [5]中国科学院大学,北京100049

出　　处：《地学前缘》2023年第2期272-281,共10页Earth Science Frontiers

基　　金：国家自然科学基金-中国地震局地震科学联合基金项目(U1839207);国家自然科学基金项目(41974105);上海市科委科研计划项目(19dz1200200);上海佘山地球物理国家野外科学观测研究站基金项目(2020z02)。

摘　　要：沂沭断裂带是华北克拉通东部的重要断裂带,历史上发生过8(1/2)级强震,区域速度模型研究可以提升地震震动图精度以及地震烈度速报的准确性,有助于防御未来的巨震,降低震害损失。本文搜集了沂沭断裂带及其邻近区域2008—2020年的数字地震波数据,经过数据降丛集化、走时数据正态分布筛选等处理得到了地震事件震中参数和走时震相数据。基于FMTOMO方法,反演得到了沂沭断裂带地壳三维速度结构。反演结果显示,在近地表地层,速度分布特征与地表地质构造单元存在密切联系,褶皱带和基岩出露区域常常呈现高速速度分布,含较厚土层的凹陷或海域区域则一般呈现低速速度分布;在中地壳地层,速度分布特征与地震活动性有密切的联系,地震震中往往密集分布于高速和低速的过渡区域。在莫霍面深度,沂沭带的速度分布呈现了分段性差异特征,且两侧的速度分布存在差异。这可能意味着断裂带深达地幔的现象。且在沂沭带中南段区域,存在高速速度分布特征,这可能与区域地幔物质上涌有关,也可能构成强震的孕震背景。郯城区域从地表至地幔顶部均显示高速速度异常,该区域会积累高应力,可能发生8级以上地震,推测其复发周期应该很长。The Yishu Fault zone is an important fault zone in the eastern North China Craton and historically experienced a magnitude 8(1/2) earthquake.To protect against future strong earthquakes and reduce earthquake damage,it is helpful to study the regional seismic velocity model so as to improve the accuracy of seismogram and rapid reporting of seismic intensity.In this study we collect digital seismic data recorded between 2008-2020 in the Yishu Fault zone,and preprocess the data using declustering and normal distribution travel-time selection techniques to obtain the local epicenter parameters and travel-time data;then by tomographic inversion using FMTOMO software we obtained three-dimensional seismic velocity model of the Yishu Fault zone.According to the 3D model,the velocity distribution features in the near surface layer are closely related to the geological structural units,as the fold belt and bedrock outcropping areas often present high velocity distribution while low velocity distribution is generally associated with the sag or sea area with thick soil layers.In the middle crustal layer,seismicity is closely related to the velocity distribution features,and the earthquake epicenters are often densely distributed in the transition zone between high and low velocities.At the Moho depth,velocity distribution in the Yishu belt shows segmental differences and differs on both sides of the belt,this could mean that the fault zone reaches the mantle.High velocity distribution is present in the middle and southern part of the Yishu belt,which may be related to the regional upwelling of mantle material,or may constitute the seismogenic background of strong earthquakes.In the Tancheng area,high velocity anomalies are observed from the earth’s surface to the top of the mantle,suggesting that high stress could accumulate in this area,and an earthquake of magnitude 8 or above might occur,but the recurrence period is considered very long.

关 键 词：山东 沂沭带 P波 层析成像 

分 类 号：P315.2[天文地球—地震学]