Lightning activities associated with 308 M≥ 5.0 earthquakes in Taiwan during 1994-2003

Abstract:

Earthquake lights and luminous phenomena are spectacular features, which have been often observed and reported. It has been known that the crust deformation activates and releases gases/charges which generate the atmospheric electric field and currents possibly resulting in luminous phenomena before and during large earthquakes. The lightning activity has been known to be one of key parameters understanding the atmospheric electric field near the Earth’s surface. However, lightning activities during large earthquakes have not yet been studied and reported. It is found that lightning activities significantly increase 3-8 and 20-30 days before the 21 September 1999 Mw7.6 earthquake. A statistical analysis has been conducted to study lightning activities over the epicenter 30 days before and after 78 land and 230 sea M≥5.0 earthquakes in Taiwan during 1994-2003. We find that lightning activities over the epicenter occur more frequently few days before the land earthquakes which is termed pre-earthquake lightning anomaly (PELA). For earthquakes with larger magnitudes, the PELA appears more frequent and expands a larger area from the epicenter. Our results confirm that the PELA associated with the M≥6.5 land earthquakes with the depth less than 20 km and 18 cumulative days meet the significant level 0.05. These suggest that for the PELA, the Earth’s surface deformation plays an important role during the earthquake preparation period. We anticipate our study to be a starting point for developing lithosphere-atmosphere coupling model of earth system sciences.