Characteristics of spatio-temporal distribution of groundwater level's change after 2016 Gyeongju earthquake. Journal of the Geological Society of Korea

Change of groundwater levels bet ore and after Gyeong-ju earthquake is analyzed for 12 monitoring wells (with 1 hour interval observations) in Gyeong-ju region. The pattern analysis of groundwater level time series shows that the iising and maintaining features of groundwater levels after the main earthquakes exist at three wells and the falling and maintaining features exist at one well. The principal component analysis shows that a new principal component, which signifies an increase of water level, is produced after the earthquake and three wells have this component features distinctly. Recession curve analysis of groundwater levels also explains that the increasing characteristics of water levels are fairly reflected at three wells and a pattern change of recession curve between pre- and post-earthquake occurs at one well. As a result, four groundwater monitoring wells show the trend of increasing or decreasing ofwater levels considerably, which are mostly located at the trigger zone of the Coulomb stress field and affected by the earthquake. More detailed analysis is required for the monitoring wells to reveal the effect of the earthquake considering a minor change of groundwater level without a rainfall effect.