郯城—庐江断裂带北段现今活动习性及地震危险性分析

Analysis of current activity and strong seismic risk on the northern part of Tancheng-Lujiang fault zone

根据最近38年的地震资料,应用b值空间分布及多地震活动参数值组合的分析方法,分析了郯城—庐江断裂带北段各次级段落的现今活动习性,判别出潜在的强震、中强震危险段落。结果表明:郯城—庐江断裂带北段存在着4个具有不同现今活动习性的次级段落,其中,渤海中南段断层面现今活动习性处于中等应力背景下的相对闭锁状态,以小地震滑动为特征,应属于有一定应变积累的潜在强震危险段落;沈阳—昌图段断层面现今活动习性处于偏高应力背景下的相对闭锁状态,以稀疏小地震滑动为特征,有长期的应变积累,是未来最有可能发生中强震的段落;营口—海城段于1975年发生了7.3级强震后余震活跃,现处于震后震源断层面应力调整阶段,出现低-b值,高应力状态,以频繁中小地震滑动为特征,因此,短期内不可能再复发强震;辽东湾段落,其现今活动习性均具有偏低应力水平,以稀疏小震滑动为特征,未来不太久的时期内复发中强以上地震的可能性较小。

According to the latest seismic datum over past 38 years,using b-value spatial distribution combines several other seismic activity parameters,we analyse the activity on each segment of the Tancheng-Lujiang fault zone,and find out the strong and medium strong earthquake potential segments.The result indicates that there are 4 sub-segments of different activity in the northern segment of Tancheng-Lujiang fault zone,in which,middle south Bohai sea segment is in a locking position under middling stress background with the main characteristic of small earthquake sliding,belonging to a strong earthquake potential segment with certain strain accumulation;Shengyan-Tuchang segment is in a locking position under higher stress background with the main characteristic of fewer small earthquake sliding,belonging to a strong earthquake potential segment with long-term strain accumulation;Yingko-Haicheng segment is active after the 1975 Ms 7.3 earthquake,so this segment is in a stage of post-earthquake hypocenter stress adjustment with low b-value and high stress state,the main characteristic of this segment is frequent medium and small earthquake sliding with lower earthquake risk in near future.Liaodong Bay segment is under a low stress background with the main characteristic of fewer small earthquake sliding,and then,in a lower probability of medium and strong earthquake risk.Under low stress background with small earthquake sliding,the Liaodong Bay segment is in low strong earthquake potential.