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.