Pilot scale groundwater monitoring network for the earthquake surveillance and prediction study in Korea

The damage caused by earthquakes have been raised in the recent years, and it is expected to increase further as the urbanization and densely populated areas expand. Therefore, the countries located on the seismically active zone are preparing and conducting various activities to minimize the earthquake hazards. The attempt on the earthquake surveillance and prediction/forecasting is the one of them. Although there is skepticism toward the likelihood of a predictive success, the preparation based on earthquake forecasting is expected to be helpful to the people living in the area. The groundwater monitoring system have been operated in some countries such as China, Japan, and Taiwan to prepare and observe damages by earthquakes, combined with the other precursors.

In Korea, the seismic hazards were not significantly conceived before M5.8 Gyeongju earthquake in 2016, which is the largest earthquake since instrumental monitoring started. The magnitudes of most of the earthquakes range between 2 and 3, and 67.6 events were occurred annually. However, the public began to be afraid of great earthquakes occurred in neighboring countries, and the M5.8 Gyeongju and M5.4 Pohang earthquake in Korea. Then, we have established a pilot-scale groundwater monitoring system along and nearby Yangsan fault zone, known to be active along the southeastern border of the Korean peninsula, to monitor the development of the further earthquake and to examine the possibility of earthquake prediction from the groundwater monitoring.

Presently, the monitoring network consists of seven monitoring wells. One was installed in 2010, while six other monitoring wells were deployed between 2018 and 2019. Each well was designed to monitor groundwater changes at the specific depth considering the geological setting and equipped with an automatic data-logger to record water level, temperature and electric conductivity in every minute. The collected data are sent to the server in the lab, once in an hour through the remote transmission unit. We found that there were precursory water-level changes before the Gyeongju earthquake and an aftershock of Pohang earthquake in the well installed in 2010.

In this study, we present the up-to date monitoring results and discussion on the precursor-suspected abnormal changes observed in 2018 and 2019.