摘要
强震前孕震体环境由于应力变化引起介质电导率等电磁性质的改变,区域地磁场垂直分量日变曲线会出现相位和幅度变化,地磁加卸载响应比是识别幅度异常的有效方法。计算了南北地震带及邻区18个显著地震事件前震中周边地磁台站垂直分量加卸载响应比,分析了地震前后地磁加卸载响应比时空分布特征及产生机理。研究结果显示:(1)在排除空间天气、台站周边观测环境、仪器及监测系统等因素的前提条件下,部分中强地震前,地磁加卸载响应比出现异常,占比44.4%。(2)地磁加卸载响应比阈值受纬度影响,同经度条件下,纬度越大、阈值越小;经过反复调试与对比,计算结果显示南北地震带北段响应比阈值为3.0、南段及西南地区为3.1。(3)一般情况下,异常出现后6个月内,发生中强以上地震,异常台站数量越多,对应的地震震级越大;中强地震震中位于阈值线附近可能性较大。
Electromagnetic properties change indielectric conductivity due to stress changes before the earthquake may cause the corresponding changes in phase and amplitude of regional vertical magnetic field diurnal variation curve,and hence geomagnetic load-unload response ratios an effective method for identification of abnormal amplitude.This paper calculates geomagnetic load-unload response ratios before 18 significant earthquakes in the north-south seismic belt,analyzes the geomagnetic load-unload response ration spatial distribution characteristics and the formation mechanism before earthquakes.The results indicate that：（1）In the exclusion of space weather,surrounding environment instrument and monitoring system and other factors,geomagnetic load-unload response ratio abnormal appearr before some strong earthquakes,accounting for 44.4%.（2）Geomagnetic load-unload response ratio threshold is affected by latitude,and in the condition of the same longitude,the greater the latitude,the lower the threshold.After repeated debugging and contrast,the calculation results show that the response ratio threshold of the north-south seismic belt in the northern section is 3,and that of south and southwest regions is 3.1.（3）In general,abnormal within 6months after the occurrence of moderate earthquakes,the bigger the number of abnormal stations,the greater the magnitude of strong earthquakes.The epicenter is more likely to belocated near the threshold line.
作者
戴苗
冯志生
刘坚
李德前
魏贵春
申学林
Dai Miao Feng Zhisheng Liu Jian Li Deqian Wei Guichun Shen Xuelin(Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China Earthquake Administration of Hubei Province, Wuhan 430071, China Earthquake Administration of Jiangsu Province, Nanjing 210014, China)
出处
《地质科技情报》
CSCD
北大核心
2017年第4期222-227,249,共7页
Geological Science and Technology Information
基金
中国地震局地震监测
预测
科研三结合课题(161704)
中国地震局震情跟踪专项工作任务(2016010411)
关键词
地磁加卸载响应比
日变幅
异常指标
地震预报
南北地震带
geomagnetic load-unload response ratio
daily variation amplitude
abnormity index
earthquake prediction
north-south seismic belt
