Researchers showed that the 1995 Kobe (Hyogo-ken Nanbu) earthquake, which struck southern Hyogo Prefecture, may have been triggered by deep underground flooding beneath Arima Hot Springs. By analyzing the stable isotope ratios of hydrogen and oxygen as well as chloride ions in Arima hot spring water over several decades, the researchers have uncovered a likely connection between the earthquake and water originating from the subducting Philippine Sea Plate.