采用空间相关法计算了1987～2013年广西邕宁地震台和河池地震台的地磁Z分量日变化幅度相对海南琼中地震台的空间相关系数,分析了研究时段内空间相关曲线异常变化特征与广西及北部湾海域中强地震的关系。结果 表明,广西及北部湾海域中强地震通常发生在邕宁地震台和河池地震台的空间相关曲线同步出现低值异常持续过程中或异常结束后3个月内,且低值异常持续时间超过1个月、异常最小幅值≤0.9。预报效能检验结果显示,该方法对广西地区M≥4.4地震具有较好的映震效果,可为该地区短临地震趋势分析提供定量判据。
The spatial-correlation method was applied to calculating the spatial-correlation coefficients of the daily geomagnetic variation data in Z component at Yongning Seismic and Hechi seismic Station in Guangxi Province relative to the geomagnetic data in Z component at Qiongzhong Seismic station in Hainan Province from 1987 to 2013. Then the relationship between abnormal variation of the spatial-correlation curves and the moderate and strong earthquakes in Guangxi and its adjacent Beibu Gulf was analyzed. The analysis suggests that the moderate and strong earthquakes in Guangxi and its adjacent Beibu Gulf usually occurred on the following conditions:the spatial-correlation curves appeared simultaneously in the process of low-value anomaly or three months after the anomaly ended,and low-value anomaly lasted more than a month and the minimum amplitude of abnormal value was less than or equal to 0.9 at Yongning Seismic Station and Hechi Seismic Station. The prediction efficiency test proved that the spatial-correlation method,which has a good effect of predicting M≥4.4 earthquakes in Guangxi region,is able to provide quantitative identification for short-term and impending earthquake prediction.
