2021年漾濞M_(S)6.4地震序列前后震源参数  

Research on Source Parameters of Earthquakes before and after 2021 Yangbi M_(S)6.4 Earthquake

作　　者：秦敏[1] 杨晶琼[1] 缪素秋 李丹宁[1] 张会苑 QIN Min;YANG Jingqiong;MIAO Suqiu;LI Danning;ZHANG Huiyuan(Yunnan Earthquake Agency,Kunming 650224,China)

机构地区：[1]云南省地震局,昆明650224

出　　处：《华北地震科学》2023年第2期81-89,共9页North China Earthquake Sciences

基　　金：云南省地震局科技专项课题(2021YBZX02)、传帮带课题(cq2-2021002);国家重点研发计划(2021YFC3000703-01)。

摘　　要：利用漾濞地区共22个固定和流动台站记录到的数字地震波形资料,在扣除地震波衰减与台站场地响应后,联合反演计算得到2021年漾濞M_(S)6.4地震序列前后共819次M L≥1.0地震的震源参数,并对M L2.9~3.8地震应力降的时空演化过程进行分析。结果显示:①漾濞地震序列的地震矩与震级相关性较好,与破裂尺度之间存在一定的正相关关系,与拐角频率之间呈现出负相关关系,对于M L≤2.8的地震,应力降随震级增大而增大,而对于M L>2.8的地震,其应力降随震级的变化趋势并不明显;②漾濞M_(S)6.4地震序列前后的应力降受漾濞区域复杂构造环境背景的控制表现明显的分段特征,在前震序列阶段,震源区中段应力降有逐渐增强的趋势,处于应力加速积累的过程,一系列高度丛集的中小地震活动所造成的应力扰动可能导致了震源区北段漾濞M_(S)6.4主震的发生;M_(S)6.4主震发生以后,其余震序列活动自北西段向南东向破裂了整个余震区,余震区北西段由于主震的发生,该区域应力背景快速调整,应力降的时空分布表现为高值-低值起伏的状态;余震区中段至最大前震震中附近区域可能由于前震活动频繁,应力释放较多,表现为应力降相对低值区域;余震区南段则余震活动丰富,为应力降高值分布区域。漾濞地震序列中震级较大的地震活动与应力降高值区域一致性较好。Based on the digital waveform data recorded by 22 fixed and temporary stations located around the Yangbi area,the inelastic attenuation coefficient and site response of 22 stations are calculated by the Atkinson method and Moya method.Source parameters of 819 earthquakes with ML≥1.0 before and after 2021 Yangbi M_(S)6.4earthquake sequence are accurately calculated after removing the effects due to earthquake inelastic attenuation and site effect.The results show that:(1)There is a good linear relation between seismic moments M0 and local magnitude ML;the source rupture radius range have a certain positive correlation with M0;the corner frequencies negatively correlated with M0;when ML≤2.8,the stress drops increase with ML,while when ML>2.8,there is no obvious relationship;(2)The temporal and spatial evolution process of stress drops derived from seismic data with ML2.9 to 3.8 shows that the spatial distribution of the stress drops before and after Yangbi M_(S)6.4earthquake sequence has obvious difference,mainly controlled by the respective seismogenic fault in Yangbi area.In the foreshock sequence,the stress drop in the middle part of the focal area shows a trend of increasing gradually,which is in the process of accelerating stress accumulation.The stress disturbance caused by a series of highly clustered moderate seismic activities may trigger the Yangbi M_(S)6.4mainshock in the northern part of the source area with long-term stress accumulation.The results indicate that the temporal and spatial evolution process of stress drops of foreshock sequence has a certain indication effect on the occurrence of the M_(S)6.4mainshock.After the M_(S)6.4mainshock,its aftershock activity broke the whole aftershock region from the northwest to southeast.Due to the occurrence of the mainshock in the northwest section of aftershock region,the background stress in this region was enhanced,and the spatial and temporal distribution of stress drop showed a high-low value fluctuation state.The area from the middle of aftershock

关 键 词：漾濞M_(S)6.4地震 震源参数 应力降 前震序列 余震序列 

分 类 号：P315.3[天文地球—地震学]