摘要
我国自1967年开展视电阻率定点连续观测以来,在观测站400 km左右范围内共发生16次/组M_(S)7.0以上地震.通过文献调研和历史观测数据梳理发现,在其中12次/组地震前视电阻率呈现出了中短期下降/上升异常变化;采用断层虚位错模式,将地震同震位错按大小相等但方向相反的方式进行加载,获取地震前震源区附近相对的介质变形特征和空间分布.计算结果显示,呈现下降变化的观测站位于地震发生前的挤压增强区域,而呈现上升变化的观测站则位于相对膨胀的区域.实验室内岩石物理实验和野外原地实验结果、以及含裂隙介质电阻率模型分析表明,含水岩土介质电阻率在压应力作用下呈现下降变化,应力卸载过程中呈现上升变化.因此,分析认为12次/组M_(S)7.0以上地震前的视电阻率变化,可能与地震晚期孕育过程之间存在“介质变形-电阻率变化”机制上的联系.
Since the fixed continuous observation of apparent resistivity was carried out in China in 1967,16 times/groups of earthquakes of M_(S)≥7.0 occurred within the range of about 400km around the monitoring stations.In this paper,through literature investigation and historical observation data analysis,it is found that apparent resistivity shows a medium-short term decline/rise changes before 12 times/groups of earthquakes.By using the fault virtual dislocation model,the coseismic dislocations are loaded in a way that is equal in size but in the opposite direction,in order to obtain the relative deformation characteristics and spatial distribution of the medium near the source region before the earthquakes.The results show that the stations showing decline changes were located in the compression region before the earthquakes,while the stations showing rise changes were located in the area of relative expansion.The results of petrophysical experiments in the laboratory and in-situ experiments in the field,as well as the resistivity constitutive relation of cracked medium show that the resistivity of water-bearing geotechnical medium decreases under compressive stress and increases during stress unloading.Therefore,it is considered that there is a possible mechanism of“medium deformation—resistivity change”between the anomalous variations of apparent resistivity before the 12 times/groups of earthquakes of M_(S)7.0 and above,and the late seismogenic processes.
作者
解滔
薛艳
卢军
XIE Tao;XUE Yan;LU Jun(China Earthquake Networks Center,China Earthquake Administration,Beijing 100045,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第8期3064-3077,共14页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(42104075)
国家重点研发计划(2017YFC1500502)联合资助.
关键词
视电阻率
7级大震
变化机理
虚位错模式
震源机制解
中国
Apparent resistivity
Earthquakes of M_(S)≥7.0
Change mechanism
Virtual dislocation model
Source mechanism solution
China
