The 2022 Mw6.2 Pasaman, Indonesia, Earthquake and Its Implication of Seismic Hazard in Central-West Sumatra

Abstract

On February 25, 2022, the Mw6.2 “Pasaman Earthquake” took place in central-west Sumatra in association with activity in the Sumatran Fault system. This study clarifies the spatial and temporal distribution of the Pasaman Earthquake sequence and forecasts the earthquake sequence’s impact on the seismicity in the vicinity and in the Sumatran Fault system. We first examined the seismicity before the mainshock and observed significant low b-value anomalies both in time and space, shedding light on the earthquake precursor by monitoring b-values prior to the event. Based on the first 18-day aftershocks, we modelled the temporal distribution of the mainshock according to the modified Omori’s law, which suggested this sequence could last 37 or 451 days. To understand the spatial pattern of the aftershocks, we calculated the coseismic Coulomb stress change imparted by the Pasaman Earthquake mainshock. The stress increase extended northwest and southeast, consistent with aftershock distribution. We further evaluated rupture probability for each segment of the Sumatran Fault. Considering the stress perturbation imparted by the Pasaman Earthquake, we expected a seismicity rate increase of ca. 40% at the Sumpur and Sianok segments in the short term. To quantify long-term rupture probability, the recurrence interval and the time elapsed since the previous earthquake were incorporated based on the time-dependent Brownian Passage Time (BPT) model. A high rupture probability is expected for a segment with a short recurrence interval and/or long time elapsed since the last earthquake. The earthquake probability at the Sumani segment in the coming 50 years was determined to be 72.0%. The outcomes of this study are the be-all and end-all for subsequent probabilistic seismic hazard assessment for not only Sumatra, but also certain metropolises in Malaysia and Singapore.

Kajian Seismik Mikro untuk Memahami Proses Aktivitas 8 Sesar di Jawa Barat

“…Jawa Barat, yang terletak di wilayah seismik aktif, menghadapi risiko inheren yang terkait dengan beberapa jalur patahan. Memahami konteks geologi dan sejarah glasiasi di wilayah ini sangat penting untuk mengembangkan strategi mitigasi risiko gempa (Wulandari et al, 2022). Studi sebelumnya telah menyoroti perlunya penilaian bahaya seismik yang terperinci di Jawa Barat, dengan mempertimbangkan karakteristik spesifik dari setiap sesar (Ramdani et al, 2023).…”