Identification of Active Faults in Lahat and Empat Lawang Region, South Sumatra Province, Based on Seismicity and Focal Mechanism Analysis

Abstract

The BMKG earthquake catalog data for the 2014-2022 period shows seismic activity in the Gumai Mountains, South Sumatra, which is located southeast of the Ketaun Segment, east of the Musi Segment, and north of the Manna Segment. Seismic activity in this area is important to study as an early indication of the presence of other active fault segments that have not been identified before. Re-analysis on the P and S wave phases picking was carried out for the 26 earthquakes in the period of 2014 to 2022 to ensure the quality of the data used in the processing. The double-difference method was then used to relocate the hypocenter of the earthquake based on a local velocity model to identify an active fault segment lineation in the area. In addition, waveform inversion method was used to obtain the focal mechanism for 7 earthquakes which were successfully analyzed to identify the fault plane direction. By combining the results of seismicity and focal mechanism analysis, we concluded that there are 3 fault segments that have not been identified before. These segments are thought to be strongly responsible for seismic activity in Gumai Mountains in Lahat and Empat Lawang Regencies, South Sumatra, which we determine to be part of the Great Sumatran Fault network.