COSEISMIC DEFORMATION ANALYSIS OF THE 2022 M6.1 PASAMAN EARTHQUAKE USING GPS DATA

• Main Author: Apriani, Medina
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/73852
• Institution: Institut Teknologi Bandung

The Pasaman earthquake occurred at 08:39:29 WIB on Friday 25th February 2022. Based on information from the USGS, the earthquake had a magnitude (M6.1) with the location of the epicenter located north of Mount Talamau at coordinate 100.1006°E-0.219°N and at a depth of ?4km. Furthermore, the main earthquake event (mainshock) was preceded by an initial earthquake (foreshock) at 08:35:51 WIB, with a magnitude of M5.2 at coordinates 99.99?E– 0.14? North, which was 18 km northeast of Pasaman and at a depth of 10 km. This thesis consists of five stages of analysis. The first is analyzing the time series graph in order to see coseismic deformation patterns. Second, calculating the displacement at each GPS station based on the direction and magnitude of the displacement vector during an earthquake. Third, determining the coseismic slip distribution. Fourth, calculating the moment magnitude of the earthquake. Fifth, analyzing the Sumatra fault segment which causes the Pasaman earthquake in 2022. The largest coseismic displacement value occurs at the CPSM station, which is ?2 cm. Moreover, the coseismic displacement of each GPS station is consistent with the displacement of the Sumatra fault, namely right lateral strike-slip. The first model uses a fault with a size of 36 km ? 16 km and a strike of 319?. From these faults, the size of sub-faults is 8 km ? 4 km. The maximum slip distribution in Model 1 occurs at a depth of ?4 km of ~14 cm which is located at coordinates 100.017? E – 0.133? N. The second model uses a fault with a size of 123 km ? 36 km and a strike of 327?. Therefore, from these faults, the sizes of sub-faults are 8 km ? 25 km, 8 km ? 23 km, and 8 km ? 5 km. Meanwhile, the maximum slip distribution in Model 2 occurs at a depth of ?4 km of ~16,3 cm which is located at coordinates 100.031? E –0.177? N. This study shows that the model which has the smallest error is Model 1 with a misfit 0,56, along with an earthquake seismic moment of 1,58 ? 1025 N m, or the equivalent of an earthquake moment magnitude of M6.1. In addition, the RMSE Model 2 is 0,88 mm with a moment magnitude of M5.8. In addition, analysis of the earthquake slip area shows that the Pasaman earthquake in 2022 occured in the Kajai segment that is the continuation of the Sianok segment in the north.