Updated Segmentation Model and Cummulative Offset Measurement of the Aceh Segment of the Sumatran Fault System in West Sumatra, Indonesia

Abstract

Sumatran fault in western Indonesia is one of the largest strike-slip fault in the world. The fault was formed as a result of the slip partitioning of the oblique convergence between the Indo-Australian and Eurasian plate along the Sunda trench. The right-lateral movement of the fault is accomodated by 19 fault segments that dissects the entire Sumatra island. We study the Aceh fault segment, which is located at the northernmost parts of the fault. The Aceh fault segment spans 250 km long passing through three districts: West Aceh, Pidie Jaya, and Aceh Besar and is affecting a total of ~546.143 population in the area. The current segmentation model assumes that Aceh fault segment acts as a single fault segment, which would generate closer to a M8 earthquake. This estimation is inconsistent with the ~M6-7 historical earthquake data. We conduct a detailed active fault mapping using the ~8 m resolution digital elevation model of DEMNAS and the sub-m DEM data from UAV-based photogrammetry to resolve the segmentation model of this fault. Our study indicate that the Aceh fault segment can be divided into 8 subsegments: Beutong, Kuala Tripa, Geumpang, Mane, Tangse, Jantho, Indrapuri, and Pulo Aceh. The fault kinematics identified in the field is consistent with right-lateral faulting. We measured cumulative displacement of geomorphic features (channels and ridges) ranging from 12.7 to 1931 m at some area. Findings of our study provide better estimation of the fault geometry and the maximum magnitude of potential earthquake along the Aceh fault segment as well as recommendation of prospective sliprate study sites. These informations are important for the development of seismic hazard analysis of the area.