丽江与芦山两次M_(S)7.0地震震例回溯研究及亚失稳特征探讨  

A Retrospective Study of Two M_(S)7.0 Earthquakes in Lijiang and Lushan and Discussions on the Characteristics of Meta-instability

作　　者：李腊月[1] 尹海权[1] 马伶俐[2] 李智蓉[3] 张超[1] LI Layue;YIN Haiquan;MA Lingli;LI Zhirong;ZHANG Chao(The First Monitoring and Application Center,China Earthquake Administration,Tianjin 300180,China;Crustal Deformation Observation Center of Sichuan Earthquake Agency,Ya'an 625000,Sichuan,China;Yunnan Earthquake Agency,Kunming 650224,Yunnan,China)

机构地区：[1]中国地震局第一监测中心,天津300180 [2]四川省地震局地壳形变观测中心,四川雅安625000 [3]云南省地震局,云南昆明650224

出　　处：《地震研究》2023年第4期461-472,共12页Journal of Seismological Research

基　　金：国家重点研发计划项目(2018YFC150330506);中国地震局震情跟踪课题(2020010223,2022010209).

摘　　要：基于川滇地区的跨断层观测资料,采用多种形变分析方法,针对川滇地区监测状况较好的1996年丽江、2013年芦山两次M_(S)7.0地震开展震例回溯研究,并以亚失稳理论及实验室结果为指导,归纳总结跨断层观测获得的断层运动在亚失稳阶段的时空变化特征及可能的表现形式,寻找区域范围内断层运动协同化现象,探索地震进入亚失稳状态的跨断层识别标志。结果表明:两次地震前,震源区在震前数年主要表现为弱变形的状态,可能是孕震晚期发震断层闭锁、断层近场应力应变积累趋于极限的表现。震源区边缘附近300 km范围内在震前数月至3年出现显著的断层形变异常,断层活动具有协同化现象,但仅个别跨断层场地观测到了与实验室岩石破裂失稳过程类似的图像,大多数场地仅仅观测到了稳态(线性阶段)、亚稳态(偏离线性阶段)特征,亚失稳态特征并不清晰,分析可能与跨断层场地所处的构造位置及观测周期有一定关系。The cross-fault observation had been conducted in the epicentral areas of the Lijiang M_(S)7.0 earthquake and the Lushan M_(S)7.0 earthquake before the two earthquakes occurred.According to the deformation analysis methods,and using the cross-fault observational data,we do a retrospective study of the two earthquakes.Guided by the meta-instability theory and on the basis of the laboratory results,we summarize the characteristics of the fault motion varying in time and space,and fault motion's possible manifestations in the meta-instable stage,to identify the synergy of fault activities in the study area,and to explore the signs obtained by the cross-fault observation which indicates that the potential earthquake has entered a meta-instable state.The results show that before the Lijiang and Lushan M_(S)7.0 strong earthquakes,the epicentral areas were mainly in a weak-deformation state with a small rate of activity.This may suggest that the seismogenic fault was locked in the late seismogenic stage,and the accumulation of the stress and strain of the fault in the near field was reaching limit.Three years before the earthquake,significant anomalies of the fault deformation occurred in the 300 km range of the epicentral area,and the anomalies lasted till several months before the earthquake.The fault activity performed a significant synergy.On some cross-fault sites,images similar to the laboratory rock rupture and instability process have been observed.On some sites only the steady state(linear stage)and meta-stable state(deviation from the linear stage)were observed.The meta-instable characteristics on these sites were not clear.We believe that this may be related with the tectonic position of the cross-fault sites and observational periods.

关 键 词：丽江M_(S)7.0地震 芦山M_(S)7.0地震 跨断层观测 震例回溯 亚失稳特征 川滇地区 

分 类 号：P315.7[天文地球—地震学]