Explosion mechanism and volume estimation of volcanic ash during the eruption of Sinabung Volcano on February 19, 2018: Insight from kinematic GPS and seismic data

On February 19, 2018, Sinabung Volcano erupted explosively, destroying the lava dome and producing a new crater. This eruption was the largest one since it became active again in 2010. We processed kinematic GPS observation combined with seismic data to analyze the explosion process and calculate the volume change during the deflation stage. The time series from the results of GPS data processing for 12 min shows a pattern of inflation that lasts for 180 s followed by deflation. Observation data is divided into 3 phases of activity. The first and second phases are inflation with pressure source during eruption at a depth of 2.3 km below the summit, followed by the third phase of deflation at a shallow depth. The hypocenter of explosion earthquake also in the depth of 2.3 km beneath the crater. This study provides information about the magma dynamics during and after the eruption of Sinabung Volcano. The volume change of inflation and deflation calculated approximately 3 x 106 m3 and - 2.2 x 106 m3, respectively. The ash weight produced by the February 19, 2018 eruption from seismic and ground deformation during the deflation period is approximately 5.6 million tons or 0.006 km3, equivalent with VEI 2 Sinabung eruption.