Two earthquake events on the Pamsoa Segment of the Matano Fault, Sulawesi

Abstract

Sulawesi Island crossed by the importance active faults of the Palukoro Fault in the western part and the Matano Fault in the eastern part. Pamsoa Segment, the fourth of six-segments of the Matano Fault (from west to east), located near importance Sorowako mining city, Sulawesi. Pamsoa segment has a 38 km length, oriented N295°E, and has an obvious 475 m sinistral river offset. A reconnaissance survey conduct in this segment along the fault crosses the mining dirt road. Two fault rupture existed on the Holocene river terrace. Accelerated Mass Spectrometry (AMS) carbon dating shows age about 5218 BP and 4446 BP on the soil samples. Nice slicken-side on red soil shows as a fresh fault rupture. This rupture shows a possible two earthquake event on the Pamsoa Segment. The Matano fault has potency similar to the 2018 Palu earthquake. If the fault has similar multi fault rupture earthquake characteristic, the Matano Fault is also classified as a Magnitude 7+ class earthquake. Further research is needed to get precise earthquake geology parameters and ideal charcoal samples.