Abstract: A series of electromagnetic anomalies have been detected at the Chongming station in ultra-low frequency band ( ULFB) befo re the Taiw an earthquake ( M =7.5, March 31, 2002) with the following characteristics.The earliest electromag netic anomalies appeared in advance of 24 day s before the earthquake, and the latest appeared in advance of 5 hours before the mainshock, w hose amplitude is largest.The amplitudes of the elect romag netic anomalies increased gradually approaching the mainshock and decreased after the mainshock again.The abundant info rmation of the elect romag netic anomalies appeared in advance of many af tershocks.This paper mainly discusses the relation between the elect romagnetic anomalies and the strong earthquakes.The analysis reveals that the properties of the preseismic elect romagnetic anomalies might be considered as signatures of an impending earthquake.

Key words: Taiwan MS 7.5 earthquake, Impending prediction, Elect romag netic anomalies, Signal characteristics