地震亚失稳过程中前兆异常演化的综合解释——以2014年鲁甸6.5级地震为例  

INTEGRATED INTERPRETATION ON THE PRECURSORY PROCESS EVOLUTION IN THE META-INSTABILITY STAGE OF THE EARTHQUAKE:A CASE STUDY ON 2014 LUDIAN M_(S)6.5 EARTHQUAKE

作　　者：蒋海昆[1] 邓世广 姚琪 宋金[1] 王锦红 JIANG Hai-kun;DENG Shi-guang;YAO Qi;SONG Jin;WANG Jin-hong(China Earthquake Networks Center,Beijing 100045,China;Institute of Earthquake Forecasting,CEA,Beijing 100036,China)

机构地区：[1]中国地震台网中心,北京100045 [2]中国地震局地震预测研究所,北京100036

出　　处：《地震地质》2024年第3期513-535,共23页Seismology and Geology

基　　金：科技基础资源调查专项(2023FY101503);地震动力学国家重点实验室开放基金(LED2022B05)共同资助。

摘　　要：文中以2014年鲁甸6.5级地震为例,在亚失稳实验及理论指导下,基于震前地震活动及地球物理观测资料并结合地震成核数值模拟结果,综合分析前兆异常时空演化与亚失稳过程的关系,首次提供了一个可明确佐证亚失稳阶段震源区成核、震源区附近协同化过程持续加剧的典型震例和观测事实。研究结果显示,依据大区域强震活动及流动重力观测,可判定鲁甸地震前研究区已处于高应力状态。在高应力背景判定的基础上,依据地震活动及地球物理观测前兆异常,可粗略判定鲁甸地震亚失稳过程可能起始于震前7、8个月,最突出的现象或判定指标是由震中附近小地震活跃所表征的断层应力状态由积累为主向释放为主的转变,以及由定点地球物理观测异常数量显著增加所表征的断层运动协同化现象,从地震成核的角度与成核后期核心弱化区扩张过程有关。之后至主震发生,还有2个时间节点需要关注:一是震前4、5个月,定点地球物理观测异常空间分布范围自震中附近向外围的明显扩展,显示断层变形的加速协同化;二是震前2个月之后,震中附近小地震活动开始减弱、微震活动及定点地球物理异常出现向震中的迁移收缩,与地震成核过程核心弱化区扩展之后的收缩过程相关联。The transition from the metastable state to the meta-instability stage indicates that the seismic fault has entered an irreversible deformation process and will lead to an inevitable instability(Ma Jin et al.,2014).Therefore,identifying the meta-instability stage is helpful for the judgment of short-term earthquake precursor anomalies.Under laboratory conditions,the meta-instability stage can be visually identified through stress-time curves,thus potentially predicting the occurrence of the laboratory earthquake.However,there are significant differences between field conditions and laboratory environments.Firstly,the underground medium and structural conditions in the real earthquake source region are unclear and far more complex than laboratory specimens.Secondly,the distribution of the sensors,sensor density,as well as measurement accuracy are limited by various conditions,making it impossible to construct an ideal observation environment covering the entire region.Thirdly,the loading stress cannot be directly measured,and the current actual stress state of the study area is unknown,which is the most difficult problem to solve.Therefore,under the guidance of meta-instability experiments and theories,it is a beneficial attempt to conduct retrospective studies on typical earthquake cases with relatively good observation conditions in the past,analyze the spatial-temporal evolution of different physical fields at different stages before the earthquakes,compare the observed phenomena with the characteristics and change processes of meta-instability stages obtained from experiments or theoretical research.Its final goal is to find possible characteristics or indirect criteria for meta-instability stages under field observation conditions.Therefore,taking the Ludian M_(S)6.5 earthquake as an example and under the guidance of the meta-instability experiments and theories,the paper comprehensively analyzes the relationship between the spatial-temporal evolution of precursory anomalies and the meta-instability process b

关 键 词：亚失稳阶段 应力状态变化 断层变形协同化 鲁甸M 6.5地震 小地震活动 地球物理观测 

分 类 号：P315.2[天文地球—地震学]