地磁数据处理与地震关系之探

Research on Relationship between Earthquakes and Geomagnetic Variations

研究了上海崇明、佘山和杭州这3个地磁台的观测资料在2004年4月21日南黄海ML4.0级、5月26日浙江省舟山群岛ML4.3级和11月15日南黄海ML4.6级地震前的异常变化特征,结果表明:杭州台和崇明台数字化地磁观测资料分钟值空间差值于4月14日～17日、4月30日、5月8日出现的异常信息很可能是震磁异常信息;杭州台和佘山台数字化地磁观测资料分钟值、模拟观测21时值Z分量地磁场相关系数R值分别在震前2天、24天和震前5天、15天出现了超出2σ值的震磁异常变化;崇明和佘山地磁台数字化地磁Z分量分钟值的空间差值异常信息在4月21日南黄海ML4.0级地震前后有所显示,但在5月26日舟山群岛ML4.3级地震前不太明显,可能与这两个地磁台站相距较近且震中距较近有关。

Three earthquakes of ML≥4.0 occurred in 2004 are studied in this paper, including the ML4.0 earthquake on April 21, 2004 in South Yellow Sea （32°51′N, 121°23′E） , the ML4.3 earthquake on May 26, 2004 in Zhoushan Islands of Zhejang Province （30°18′N, 122°30′E） and the ML4.6 earthquake on November 15, 2004 in South Yellow Sea （32.5°N, 123.7°E） . Based on the data recorded at the geomagnetic stations of Chongming and Sheshan in Shanghai as well as Hangzhou in Zhejiang Province, the anomaly variations of the geomagnetic field before the three earthquakes are studied. The results show that a） the anomaly variations of the spatial differential values between the Hangzhou and Chongming stations during the time periods of April 14-17, April 30 and May 8, 2004 seem to be related to the earthquakes; b） the correlation coefficients of the Z components of the geomagnetic field at Hangzhou and Sheshan stations show anomaly at 2 days, 5 days, 15 days and 24 days before the earthquakes respectively; c） the correlation coefficients of the Z components of the geomagnetic field at Chongming and Sheshan stations show abnormal variations before and after the ML4.0 earthquake, but show no obvious anomaly variations before the ML4.3 earthquake, which may be due to the short distance between the two stations as well as the short epicentral distance.