Identification of the Semangko Fault in Sumatra, Indonesia, based on gradient gravity data analysis

Abstract

The Semangko Fault (SF) is a major active fault that extends across from Aceh (in northern part) to Lampung Province (in southern part) of Sumatra Island, contributing to much deformation and high seismicity along the fault. The fault affects a pattern in the density of surrounding rocks and can be identified by the gravity method. This research aimed to determine the fault structure using gravity gradient analysis in the Lampung area. Bouguer anomalies were analyzed from satellite gravity data and gravity gradient calculation, for fault structure identification around SF. Based on the Bouguer anomalies and gravity gradient analysis (first and second-order horizontal derivatives), SF trends NW-SE. The SF is divided into two sides at the Suoh area, West and East SF sides across to Semangko Bay. That trend is confirmed with geological and topographical data analysis. These findings suggest that gravity anomaly data and horizontal gravity gradient analysis can be used to determine and identify the presence of the SF. The seismic hazard assessments can mitigate hazards to all people in the vicinity of the SF area.

Keywords

• gravity gradient
• hazard mitigation
• lampung
• semangko fault