Laboratory investigation of earthquake lightning due to landslide

Several laboratory experimental studies of photoemission characteristics of rocks as they fracture have been conducted to elucidate the mechanism of earthquake lightning (EQL). In most of these studies, granite, which exhibits remarkable photoemission, is widely used to explain the mechanism attributed to the exoelectron emission effect or piezo-induced effect of quartz, a constituent mineral of granite. Photoemission induced by rock fracturing has been observed prominently during landslides caused by earthquakes. According to the literature on historical earthquakes, landslide-induced EQL was witnessed even at locations where quartz was not present. In this study, we therefore studied the physicochemical characteristics of photoemissions associated with impact shear fractures in various rocks, selected based on historical earthquake records of landslide EQL. As a result, we could highlight various physicochemical processes associated with the frictional heating generated during shear impacts between rocks.