Deformation of West Sumatra Due to the 2016 Earthquake (M7.8) Based on Continuous GPS Data

Abstract

Sumatra Island, one of the areas in Indonesia, has a very active tectonics in the world. It causes Sumatra to be prone to tectonic earthquake disaster due to the movement of the plates around it. On March 2nd, 2016, a Mw7.8 earthquake centered in the Wharton Indian Ocean Basin Zone, West of Sumatra island happened at a depth of 24 km. This earthquake was an intraplate earthquake that occurred due to the movement in the ocean plate as a type of left lateral strike-slip fault. The calculation of deformation in West Sumatra due to the earthquake was conducted through continuous GPS observation of SuGAr (Sumatran GPS Array) from January 1, 2015 until March 30, 2017 around west part of Sumatra areas. Data processing is done by using GAMIT/GLOBK 10.6 software and the results in daily solution shows that the horizontal component of co-seismic deformation of West Sumatra earthquake in 2016 ranged from 3,6 mm – 5,5 mm which moves toward to northwest. The difference in velocity movement of GPS observation before and after earthquake is used to calculate the strain of plate tectonic around West Sumatra region, where there is a compression pattern before earthquake equal to 2.72×10-8 strain and after earthquake equal to 5.98×10-8 strain. This indicates that there is an increase in compression value in the observation after the earthquake, and the observation area again show the interseismic deformation which means that there is still a considerable accumulation of energy and sometimes can cause the other earthquake.