摘要
利用290个ML≥2.5的景谷6.6级地震序列事件的数字波形资料,计算得到其震源参数。结果显示,地震矩M0数值范围为1012~1016 N·m;拐角频率fc为3~16 Hz;视应力数值范围为0~15 MPa,平均值是2.14 MPa,中位数为1.39 MPa。同时,各个震源参数之间均存在一定的相关关系;景谷地震序列余震空间分布可分为北段、中段与南段,其视应力高低分布依次为:南段>中段>北段;表明主震发生后,震源区南段区域的应力水平最高,这可能是后续5.8级\,5.9级强余震均发生在南段的根本原因。在视应力时间变化特征方面,5.8级、5.9级强余震的发生前,震中所在的南段视应力数值存在“逐渐变大-维持稳定”的特点。而后续未发生强余震的北段和中段,其视应力时间变化为早期快速调整,后续逐渐变化到各自区域的视应力均值水平;这类变化表明对于震源区南段,在强余震发生前的短时间内,南段区域首先出现局部应力不断挤压增强,并随后维持相对高值应力水平的“闭锁”状态,直到强余震的发生。因而,震后震源区余震视应力的空间分布对强余震可能产生地点判定有指示作用,其时间变化特征与地震序列中较强地震的发生存在一定的相关性。余震视应力的时空变化对序列后续地震活动的判定有重要指示作用,可为强余震的时空判定提供相应参考。
In this paper,the digital records of 290 ML≥2.5 earthquakes recorded in the Jinggu M6.6 earthquake sequence are used to calculate source parameters.Results show that the seismic moment M0 is 1012-1016 N·m,the corner frequency fc is 3-16 HZ,the apparent stress is 0-15 MPa,the mean value is 2.14 MPa,and the median value is 1.39 MPa.A certain correlation was also found between the source parameters,and the spatial distribution of aftershocks in the Jinggu earthquake sequence can be divided into northern,middle,and southern sections.The distribution of apparent stress is south>middle>north.This finding indicates that the stress level in the southern section of the source area is the highest after the main shock occurred,which may be the root cause of the subsequent M5.8 and M5.9 strong aftershocks that occurred in the southern section.Apparent stress in the southern section is“gradually rising-maintaining stability”before the strong aftershocks occurred.In the northern and middle sections where no strong aftershocks occurred,the temporal change in apparent stress is a rapid adjustment in the early stage,which then gradually changed to the average value in each region.Such changes indicate that in a short period before the occurrence of strong aftershocks,the local stress in the southern section first increased and then maintained a“locked”state of a relatively high value until the occurrence of strong aftershocks.Therefore,the spatial distribution of apparent stress in the source area has an indication of the possible location of strong aftershocks,and its temporal variation has a certain correlation with the occurrence of strong earthquakes in the seismic sequence.The temporal and spatial variations of apparent stress have important indications for subsequent seismic activities and can provide a corresponding reference for the space-time determination of strong aftershocks.
作者
周少辉
蒋海昆
曲均浩
郑旭
郭宗斌
李亚军
张志慧
ZHOU Shaohui;JIANG Haikun;QU Junhao;ZHENG Xu;GUO Zongbin;LI Yajun;ZHANG Zhihui(Shandong Earthquake Agency, Ji’nan 250014, Shandong, China;China Earthquake Networks Center, Beijing 100045, China,)
出处
《地震工程学报》
CSCD
北大核心
2020年第6期1565-1572,共8页
China Earthquake Engineering Journal
基金
中国地震局监测、预报、科研三结合项目(3JH-201901064)
山东省自然基金(ZR2017LD009)
山东省地震局一般科研项目(YB-1902)
中国地震局星火计划项目(XH19027,XH19026Y)。
关键词
视应力
余震序列
景谷地震
强余震判定
apparent stress
aftershock sequence
Jinggu earthquake
determination of strong aftershock
