用小波法研究台湾省两次7．6级大震前后仑坪台的地磁变化

Wavelet analysis results for the geomagnetic variations of the Lunping observatory before and after two strong earthquakes

用小波法分析了台湾省两次Ms 7．6大震(1986年花莲大震和1999年集集大震)前后仑坪台的地磁变化。从小波分析得出的“日变幅差”变化看,两次大地震前一个月内都有异常变化,花莲地震前出现负异常,集集地震前出现正异常。

The geomagnetic data recorded at Lunping observatory before and after two great earthquakes, 1986 Hualian earthquake and 1999 Chi-Chi earthquake, were analyzed using the wavelet transform technique. The results indicate that the amplitudes of the diurnal variations＇, derived from the wavelet transform, appear to be anomalous during one month before the main shocks. Before the Hualian earthquake there is a negative anomalous change, and before the Chi-Chi earthquake there is a positive change.