High slip rate for a low seismicity along the Palu-Koro active fault in Central Sulawesi (Indonesia)

Abstract

In eastern Indonesia, the Central Sulawesi fault system consists of complex left-lateral strike-slip fault zones located within the triple junction area between the Pacific, Indo-Australian and Eurasian plates. Seismicity in Central Sulawesi documents low-magnitude shallow earthquakes related, from NW to SE, to the NNW-trending Palu-Koro (PKF) and WNW-trending Matano fault zones. Study of the active fault traces indicates a northward growing complexity in the PKF segmentation. Left-lateral displacement of 370 ± 10 m of streams incised within fans, whose deposition has been dated at 11 000 ± 2300 years, yields a calculated PKF horizontal slip rate of 35 ± 8 mm yr-1. This geologically determined long-term slip rate agrees with the far-field strike-slip rate of 32-45 mm yr-1 previously proposed from GPS measurements and confirms that the PKF is a fast slipping fault with a relatively low level of seismicity.