GEOMETRY AND KINEMATICS OF THE RENUN SEGMENT OF THE SUMATRAN FAULT IN NORTH SUMATRA

Abstract

The Sumatra region hosts shallow active faults, including the Sumatran Fault, resulting from oblique convergence between the Indo-Australian and Eurasian plates. This condition contributes to high earthquake activity in Sumatra, including the North Sumatra region. Recent seismic activity, a moment magnitude (Mw) 6.0 along the Renun Fault in North Tapanuli, North Sumatra, occurred on October 1, 2022. This event, followed by 124 aftershocks, highlights the seismic hazard posed by this fault. This research aims to characterize the geometry and kinematics of active faults along the Renun Fault to update the existing earthquake hazard maps for the North Sumatra region. In this study, we employ earthquake relocation and focal mechanism methods to analyze the earthquake distribution pattern and focal mechanism solutions, along with tectonic-geomorphological analysis of the Renun Fault. The focal mechanism solution indicates a dominant dextral strike-slip faulting mechanism. Analysis of the focal mechanism solutions and tectonic-geomorphological features using remote sensing reveals a dominant movement direction of the fault, from northwest to southeast (NW-SE). Based on the surface geometry, we propose that the Renun Segment can be further divided into three subsegments: Renun-A (with a length of ~187.3 km), Renun-B (with a length of 33.8 km), and Renun-C (with a length of 25.2 km), with estimated maximum magnitudes of Mw 7.74, 6.52, and 6.31, respectively.