Tectonic landform and paleoseismic events of the easternmost Matano fault in Sulawesi, Indonesia

Abstract

The 190-km-long Matano fault is a major left-lateral strike-slip fault in Sulawesi, Indonesia that accommodates the rapid westward motion of the Pacific plate relative to the Australian plate. The Matano fault has remained unruptured at least in the past two centuries. The lack of geologic information, such as precise active fault traces, paleoseismic history, and slip rates has been a significant barrier to assessing the seismic hazards of the Matano fault. This paper presents the results of tectonic geomorphic and paleoseismic investigations on the 30 km long easternmost portion of the Matano fault. We identified four geometrical fault segments, documented five surface faulting events, and calculated a surface-rupturing earthquake recurrence interval of 200–470 years and a slip rate of 21 ± 9 mm/yr. The timing of the most recent surface-rupturing earthquake was constrained between 1432 and 1819 CE with an estimated Mw ∼ 7.4 and a probable rupture length of ∼110 km. At least 200 years have passed since the latest faulting event, exceeding the shortest recurrence interval. Thus, the next surface-rupturing earthquake is already due. Integrating our interpretations with results from several published studies clarifies that the Matano fault slips slower than the Palu-Koro fault and connects to the South Sula fault in addition to the Tolo thrust.