Hypocenter Relocation Using Fast Marching Method (FMM) in Tarutung

Abstract

Tarutung is a geothermal potential region and has relatively high seismicity due to the Sumatra fault system and young arc volcanism. There were many recorded significant earthquakes occurred in Tarutung. The seismic activity proves that a good understanding of the Tarutung tectonics is necessary. This research aims to study the tectonic setting and seismic activity of Tarutung area. In this study, we used Fast Marching Method (FMM) to relocate hypocenters using the arrival time of P-wave data. This data from temporary seismic station network deployed around Tarutung and Sarulla. The seismic station network consists of 42 short-period stations that deployed in May 2011 and continued to record 10 months of seismic activity. The relocation process used global velocity model of AK135, modified AK135, and local velocity model. The results show differences in terms of hypocenter relocated using each model. By analyzing the relocated hypocenters, each result can be used to represent the crustal seismic activity and tectonic settings of this region. The Sarulla region is on the Toru fault with a vertical linear distribution of earthquakes with a dip of 900. The distribution of earthquakes is more spread out in the Tarutung area, which is a graben area. This is the result of the third velocity model with a residual travel time is 934.07 milliseconds.