1979年溧阳地震前后的转换函数变化
CHANGES IN TRANSFER FUNCTION BEFORE AND AFTER THE 1979 LI YANG JIANG SU, EARTHQUAKE
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摘要: 以余山地磁台为参考台, 对1979年7月9日溧阳6.0级地震前后的4月25日和8月13日两个磁暴事件进行非稳态技术处理, 并从中提取周期为56, 34和21分钟的地磁短周期变化的台际转换函数作地震前后的变化检验, 发现周期为21分钟的最大电磁感应主轴的转换函数数值|Tu|和方向, 在溧阳地震震中距150km内的台站上, 有不同程度的变化:|Tu|变化在溧阳台最大, 为0.190;变化在常熟台最大, 为31.这些结果如从地质构造背景上来考察, 会得到合理的解释.此外, 转换函数的方向在地震前后所显示的显著变化, 也为转换函数作为地震的可能前兆提供一定的信息.Abstract: Geomagnetic variations over three period bands 17-28, 28-41 and 43-80 min. extracted from two magnetic storms, one April 25 and the other on August 13, 1979, occurring before and after the July 9, 1979 Li Yang M6.0 earthquake, have been analysed with a special method for non-stable storm fieid. From these short period variations the maximum principal axes of induction Tu over each period band have been calculated for each station (△u| and ir direction , before and after the earthquake.The changes in |Tu| reached the greatest value (0.190) at Li Yang station (△ = 25km) and Changes in being greatest (31) at Chang Shu station (△ = 145 km). The changes in Tu at each station can be reasonably interpreted by association with the earthquake if they are put upon the local geological setting. In addition, like |Tu|, the variation in would also serve as a probable precursor prior to an intermediate-strong earthquake.
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[2] YanaKihara, K., Secular variation of the electrical conductivity anomaly in the central part of Japan, b1cm. Kakioka Mag. Obs., 15, 1——11, 1972.
[3] Yanagihara, K. and T. Nagano, Time change of transfer function in the Central Japan anomaly of couductivity with special reference to earthquake occurrences, J. Geomagn. Gcoelec., 28, 157——163, 1976.
[4] Tsuneji Rikitake, Changes in the direction of magnetic vector of short period geomagnetic variations before the 1972 Sitka, Alaska, earthquake, J. Geomagn. Geoelec., 31, 441——448, 1979.
[5] Chen P. F., A search for correlation between time change in transfer functions and seismic activity in north Taiwan. J. Geomagn. Geoelec., 33, 635——643, 1931.
[6] Woods, D .V. and F. E. M. Lilley, Geomagnetic induction in Central .lustralia, J. Geomagn. Geoelee., 31. 449——458, 1979.
[7] Klsin, D. R., J. C. Larson, Magnetic induction field (2——3cpd) on H.nwaii island and their implications regarding electrical conductivity in the oceanic mantle, Geophys. J. R, astr. Soc. 53, 61——77, 1978.
[8] 严大华, 局部地区电导率异常的地磁检测, 地震学刊, 1981, 1: 44——48,
[9] Shiraki, M., Monitoring of the time Change in transfer functions in the Central Japan Conductivity anomaly. J. Geomagn. Geoelec., 32, 637——648, 1980.
[10] Banks, R. J., Complex demodulation of geomagnetic data and the estimation of transfer functions. Geophys. J. R. astr, Soc. 43, 87——101, 1975.
[11] Gough, D. I. J. H. de Beer, Source——field bias in geomagnetic transfer functions: A case history. J. Geomagn. Ceoelee. 32, 8, 1980.
[12] 谢瑞征、陈晓明、李端璐, 傈阳六级地震的发震构造, 地震科学研究, 1981 , 4: 39——45.
[13] 孙寿成, 秦承昌, 傈阳地震的烈度, 地震战线, 1980, 1: 1——3.
[14] 刘万琴、黄家正, 用瑞雷波广义方向性函数研究5——6级地震的破裂过程, 地震学报, 4, 27——33, 1982.
[15] 叶洪、张文郁、于之水、夏勤1979年深阳六级地震震源构造的研究, 地震地质, 2, 27——37, 1980.
[16] 贺楚儒、彭纯一、张四维, 傈阳六级地震的震磁效应观测, 地震学刊, 1982, 2: 1——9.
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