Analysis of Semeru Volcano Deformation Using Static and Kinematic Solutions with GPS Data 2015-2023

Abstract Semeru Volcano is the highest peak on the island of Java. Semeru is characterized by continuous volcanic and strombolian eruptions that produce eruptive material which might result in casualties and infrastructure damage. One of them is the eruption on December 4, 2021. Therefore, to reduce the impact of future disasters, deformation monitoring using GPS is needed. In this study, we utilize GPS observation data located on Semeru Volcano and process it using GAMIT/GLOBK and TRACK. Processing is done with static solutions, kinematic solutions, and strain to determine the deformation pattern before, during, and after the December 4, 2021, eruption. The processing results of statis solution shows the pattern of displacement to the southeast in accordance with the direction of movement of the Sunda Block, with a range of 21.49 mm/year to 30.96 mm/year. The inSluence of the Sunda Block and other subduction-induced deformations were removed by referenced to CLUM station located 25 km from the volcano. The value of local velocity experienced a velocity of 1.81 mm/year to 7.83 mm/year with varying directions of movement. Kinematic processing using TRACK succeeded in showing the deformation pattern that occurred in the eruption of Semeru Volcano on December 4, 2021. Time Series in the Sirst phase (07:46:59 UTC–07:51:10 UTC) shows an inSlation and extension pattern of 0.054 m at the LEKR and 0.055 m at the SAWR station, followed by a deSlation and compression pattern of −0.018 m at the LEKR and −0.031 m at the SAWR in the second phase (07:51:10 UTC–07:56:00 UTC). The third phase (07:56:00 UTC– 08:03:00 UTC) showed deSlation and compression patterns with values of −0.058 m at the LEKR and −0.003 m at the SAWR. While using strain calculations, in the phase before the eruption, the strain was dominated by compression on the entire mountain body. Meanwhile, the phase after the eruption has a pattern that is divided into two, namely compression on the east side of the mountain and compression-extension on the southeast side of the mountain. These results are expected to contribute to understand the characteristics Semeru Volcano eruption in the future based on geodetic data.