|Cheng, Kai-Chien;Chung, Ling-Ho;Lee, Yuan-Hsi;Kao, Ricky
|Spatial and Temporal Gravity Change and Mass Redistribution at the Wandan Mud Volcano in Taiwan
|The Wandan mud volcano, classified as an intermittent one, is located in the coastal plan of Kaohsiung and Pingtung, SW Taiwan. Although its past eruptions are not regular, it has erupted at least once a year, except for 1999 and 2017. About 1 meter mud deposit covering the nearby dry farmland has been observed in one of the recent eruptions in 2015. However the irregular amount and period of eruptions and possible hazards it may cause have been little known by far. In this study, we conducted repeated campaigns of precision gravimetry to monitor the temporal gravity change once a few months since 2015 with Microg LaCoste FG5 absolute gravimeter and Scintrex CG-5 relative gravimeter. We arranged the before and after gravity measurements for eruptions. Preliminary result reveals that there’s a 30 μGal absolute gravity increase near the crater before an eruption on April 28, 2016 and a 150 μGal drop after that. The spatial feature of the absolute gravity increases in the western area and decreases in the southern part. The result confirms that the temporal gravity change and possibly the mass redistribution caused by the Wandan mud volcano is sensible to the precision gravimetry. Though some difficulties such as hydrology and other corrections need to be overcome, the promising result is anticipated to be helpful to the understanding of the activities of the Wandan mud volcano and diapirs in the area.