A Study of Lightning Activities and M>=5.0 Earthquakes in Taiwan During 1993-2002

Lightning activities near the fault zone significantly enhanced 2-7 days prior to the Chi-Chi earthquake (Mw7.7, 1747 UT, 20 September 1999). A statistical investigation of lightning activities 15 days before and after 279 M>=5.0 earthquake days occurred in Taiwan during 1993-2002 are carried out. We isolate lightning occurrences within 50km x 50km area of each epicenter 15 days before and after the earthquakes and stack for the overall 279 earthquakes, the 206 sea earthquakes, and the 73 land earthquakes. Results shows for the overall, sea, and land earthquakes that the ratios of the stack sum of the 1-15 days before to the after are 56%/44%, 50%/50%, and 65%/35%, respectively. We further examine lightning activities associated with the overall 35, the 26 sea earthquakes, and the 9 land M>=6.0 earthquakes during the same period. The ratios of the overall, the sea and the land earthquakes are 59%/41%, 48%/52%, and 77%/23%, respectively. The larger values of the ratios indicate that lightning activities before the land earthquakes are enhanced.