CHANGES IN TRANSFER FUNCTION BEFORE AND AFTER THE 1979 LI YANG JIANG SU, EARTHQUAKE

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.