中国大陆M_(S)≥6.0地震前地电阻率异常特征

Apparent resistivity changes before the earthquakes of M_(S)≥6.0 in China

我国地震地电阻率观测通过连续监测地下介质电阻率随时间的变化及其空间分布规律,服务于地震中短期预测。自1967年开展观测以来,已积累大量观测数据和中强地震前异常变化资料。通过文献调研和数据分析,系统梳理了在观测站网及附近区域发生的M_(S)≥6.0地震的地电阻率震前异常。分析发现:(1)M_(S)≥6.0地震前,具有地电阻率异常的观测站比率随震中距的增加而显著降低;(2)M_(S)6.0—6.9地震前,地电阻率异常持续时间随震级增加而略微增加,而M_(S)≥7.0地震前未出现异常持续时间随震级增加的现象;(3)M_(S)≥7.0地震前,地电阻率异常持续时间随震中距增加有所减小,但统计结果的离散度较大,而M_(S)6.0—6.9地震前则无此现象。整体而言,不同震中距范围内,地电阻率异常持续时间并未呈现较好的规律性。

China’s seismic earth resistivity observation serves the medium and short-term earthquake prediction by continuously monitoring the change of underground medium resistivity with time and its spatial distribution.Since the observation was carried out in 1967,a large amount of observation data and many abnormal changes before moderate and strong earthquakes have been accumulated.Through literature research and data analysis,this paper systematically combs the earth resistivity anomalies before M_(S)≥6.0 earthquakes in and around the observation station network.Statistical analysis shows that the ratio of observation stations with abnormal ground resistivity before earthquakes with M_(S)≥6.0 decreases significantly with the increase of epicenter distance;The duration of anomalies before M_(S)6.0-6.9 earthquakes increases slightly with the increase of magnitude,and there is no phenomenon that the duration increases with magnitude before M_(S)≥7.0 earthquakes;The duration of anomaly before M_(S)≥7.0 earthquakes decreases with the increase of epicenter distance,but the dispersion of statistical results is large,while there is no secondary phenomenon before M_(S)6.0-6.9 earthquakes.On the whole,the anomaly duration in different epicentral distances does not show good regularity.