中国大陆东部强震活动特征

Activity Characteristics of Strong Earthquakes in Eastern China's Mainland

中国大陆东部是我国地震高发地区,区域内人口密度大、经济相对发达。根据地质构造背景和地震活动的差异,将中国大陆东部划分为东北地区、华北地区、东南沿海地区和华南其他地区,选取1815年以来MS≥6.0地震目录(不包含东北深源地震)作为基础资料研究中国大陆东部强震活动特征。首先基于活动地块理论对中国大陆东部地震活动区进行划分,然后从时间和空间分布上分析中国大陆东部强震活动特征,最后预估中国大陆东部的未来强震活动趋势。研究结果表明:①中国大陆东部MS≥6.0地震主要集中在华北地区和东南沿海地区,而东北地区和华南其他地区强震活动相对较弱,同时华北地区和东南沿海地区MS≥6.0地震具有同步活跃的特征;②华北地区MS≥6.0地震的主体活动区包括华北平原活动地块、鲁东-黄海活动地块和燕山-渤海带,东南沿海地区的主体活动区为滨海断裂带、长乐-诏安断裂带和台湾海峡,东北地区的主体活动区为松辽盆地;③采用威布尔分布对1815年以来各活跃幕时段MS≥6.0地震首发和次发地震间隔进行拟合,认为未来5年中国大陆东部发生MS≥6.0地震的可能性较大。

Eastern China's Mainland is an earthquake-prone region with large population density and high level of national economic development.According to the difference of geological structure background and earthquake activities,eastern China's Mainland is divided into four regions,including Northeast China,North China,Southeast China coastal area and other areas of South China.We applied MS≥6.0 earthquake catalogue(deep earthquakes in Northeast China are not incorporated)to investigate the activity characteristics of the earthquakes in eastern China's Mainland.In this study,we discussed divisions of seismicity regions in eastern China's Mainland based on active-tectonic block theory,and then analyzed the seismic episode characteristics of strong earthquake activity distributions from time and space.Finally we evaluated the earthquake occurrence probability in future.Our main results suggest①Earthquakes of MS≥6.0 in eastern China's Mainland are mainly concentrated in North China and Southeast coastal area,and other areas are with lower earthquake activity level.Meanwhile,earthquake activities of North China and Southeast coastal area are synchronic.②The major regions of MS≥6.0 earthquakes in North China are concentrated in North China Plain block,Ludong-Huanghai block and Yanshan-Bohai seismic zone,and the major regions of MS≥6.0 earthquakes in Southeast coastal area are concentrated in Binhai(littoral)fault belt,Changle-Zhaoan fractured zone and Taiwan strait;In addition,the major regions of MS≥6.0 earthquakes in Northeast China are concentrated in Songliao Basin.③By using the Weilbull distribution function fitting time intervals between first and second MS≥6.0 earthquakes happened in eastern China's Mainland from 1815 during the seismic active periods,we found that the probability of the MS≥6.0 earthquake within 5 years is relatively great.