Investigasi Tektonik Tarutung Berdasarkan Mekanisme Fokal dan Kelurusan Distribusi Gempa yang Akurat

Abstract

On October 1st, 2022, the Mw 5.8 shallow earthquake occurred in the Tarutung region, North Sumatra, Indonesia, resulting in V – VI Modified Mercalli Intensity (MMI) scale, followed by 170 aftershocks and extensive damages. The causative fault that is responsible for the earthquake was debatable due to its location in the extensional duplex of the Renun and the Toru fault. Thus, further analysis of its source characteristics is crucial to explain the recent tectonic system in the Tarutung area. In this study, we relocated the associated hypocenters using the double difference method with an updated velocity model derived by simultaneous inversion. We determined focal mechanisms employing full waveform inversion and used the parameters to estimate the fault traces, faulting mechanism, and static stress transfer. The relocated hypocenters and focal mechanism solutions show that the Tarutung earthquake has a right-lateral faulting mechanism in the direction of 138º – 158º. The distribution of the dominant earthquake to the southeast of the main earthquake explains the direction of static stress transfer. This research proposed an updated schematic with a pull-apart system assuming a possible difference in geodetic slip rate between the southernmost part of the Renun fault and the northernmost part of the Toru fault. It also proposed a schematic of the Tarutung pull-apart system with secondary faults as part of extensional duplex indicating a negative flower structure. The results highlight an extensive analysis to provide comprehensive studies investigating the Tarutung earthquakes to support seismic hazard assessments.