Increased Stress Along the Sumpur and Northern Sianok Segments of Sumatran Fault Due to the 25 February 2022 Mw 6.1 Pasaman, Indonesia, Earthquake

On 25 February 2022, a destructive Mw 6.1 earthquake struck western Sumatra in the early hours of the morning. The earthquake shaking was focused around the Pasaman Regency and resulted in 25 fatalities. Coseismic displacements were recorded by an existing network of Global Navigation Satellite System (GNSS) sensors managed by the Geospatial Information Agency of Indonesia. The GNSS data show a maximum of 2.0 cm of displacement with a right-lateral sense of motion across a northwest–southeast-trending fault. An investigation into the responsible fault producing the earthquake is performed through a series of coseismic slip inversions on a rectangular fault plane, comparing two fault models: (a) a fault segment that is an extension of the already identified Sianok segment of the Sumatran fault zone, and (b) the recently identified Talamau segment. The maximum slip of 14 cm occurred at 4 km depth, 13 km away from the epicenter. The mainshock is associated to a seismic moment of 1.58×1025 N·m, or equivalent to Mw 6.1. Our results indicate increased stress along the Sumpur segment and the northern Sianok segment. With no historical earthquakes reported along the Sumpur and northern Sianok segments since 1892, our analysis using a scaling relationship between fault length and earthquake magnitude indicates that a rupture in these areas could potentially generate an earthquake with a magnitude of 6.7.