Influence of the Gyeongju Earthquake on Observed Groundwater Levels at a Power Plant

Abstract

Groundwater levels at a power plant site were analyzed using statistical techniques to ascertain if there was any influence from an earthquake that occurred approximately 27 km away. This earthquake was the Mw 5.5 Gyeongju earthquake that occurred on 12 September 2016 at 11:32 UTC in South Korea. Groundwater levels at five groundwater monitoring wells were examined against the 2016 Gyeongju earthquake, local precipitation, and local tide levels. A visual examination of the groundwater monitoring well data suggested no real effect or influence from the earthquake. However, precipitation data implied a rise in groundwater levels. Cross-correlation analyses also showed no significant relationship between groundwater levels and the earthquake in question. Interestingly, three of the five groundwater monitoring wells suggested a low-to-moderate correlation between groundwater and tide levels while the remaining two groundwater monitoring wells showed a low-to-moderate correlation between groundwater levels and precipitation. Granger causality tests suggested a closer relationship between tide and groundwater levels for two of the wells, questionable results describing precipitation for another two wells, and no relationship with the earthquake for four of the wells. Data resolution plays an important role in the analyses.