Foreshock–mainshock–aftershock sequence analysis of the 14 January 2021 (Mw 6.2) Mamuju–Majene (West Sulawesi, Indonesia) earthquake

Abstract

We present here an analysis of the destructive Mw 6.2 earthquake sequence that took place on 14 January 2021 in Mamuju–Majene, West Sulawesi, Indonesia. Our relocated foreshocks, mainshock, and aftershocks and their focal mechanisms show that they occurred on two different fault planes, in which the foreshock perturbed the stress state of a nearby fault segment, causing the fault plane to subsequently rupture. The mainshock had relatively few aftershocks, an observation that is likely related to the kinematics of the fault rupture, which is relatively small in size and of short duration, thus indicating a high stress-drop earthquake rupture. The Coulomb stress change shows that areas to the northwest and southeast of the mainshock have increased stress, consistent with the observation that most aftershocks are in the northwest.

Seismotectonics of Sulawesi, Indonesia

“…Nevertheless, our observations revealed an increase in seismicity along the Palu-Koro fault immediately after the 28 September 2018 (Mw 7.6) Palu earthquake. Interestingly, several zones in Sulawesi also showed increasing seismicity after this earthquake, e.g., the swarm activity in the Mamasa zone since 2 November 2018 (Supendi et al, 2019); the Mw 6.8 Tolo Bay earthquake on 12 April 2019, followed by its sequence until 2022; the earthquake sequence that occurred east side of Makassar Strait Thrust (MST) Central during 2020-2022; the 14 January 2021 (Mw 5.7 and Mw 6.2) Mamuju-Majene earthquake in the MST-Mamuju (Supendi et al, 2021); and the 26 July 2021 (Mw 5.7 and Mw 6.2) Tojo Una-Una earthquake near the extension zone of Sulawesi's East Arm (Figure 10). These observations were based on the cumulative number of earthquakes and cumulative seismic moment as a function of year, respectively (Figure 10).…”

Unmanned Aerial Vehicles for geospatial mapping of damage assessment: A study case of the 2021 Mw 6.2 Mamuju-Majene, Indonesia, earthquake during the coronavirus disease 2019 (COVID-19) pandemic

“…One of those earthquakes was the Mamuju-Majene earthquake in West Sulawesi ( Gunawan et al, 2021 ). The Mamuju-Majene Earthquake occurred in a sequence, with the foreshock occurring on Thursday 14 th January 2021, at 14:35 (local time, GMT+8) with a magnitude of 5.9 at a depth of 12.3km ( Supendi et al, 2021 ). Twelve hours after the foreshock, a mainshock occurred in the early morning of Friday 15 January 2021, at 02:28 (local time, GMT+8).…”