Relocation of volcano-tectonic earthquake hypocenter at Mt. Sinabung using double difference method

Abstract

Sinabung is one of the active volcanoes in Indonesia that located in Karo, North Sumatra. Before the eruption in August 2010, this mountain is type-B volcano and then it change to type A volcano. Since the eruption in 2010, volcanic activity still continue and hasn’t show any signs of stopping yet. Due to volcanic activity, it causes an earthquake in the body of the mountain. The type of earthquakes that is recorded at Sinabung Mountain station are deep volcanic (VT-A), shallow volcanic (VT-B), tremors earthquake, bellows earthquake, low-frequency, high-frequency, regional tectonic earthquake, local tectonic earthquakes, eruptions and earthquakes. VT-A and VT-B earthquakes are associated with the magma movement process. This study reform 1D velocity model in Sinabung Mountain and relocate the hypocenter using Double Difference (DD) method for the earthquake data from July to December 2013. The purpose of hypocenter relocation is to get the earthquake position accurately so it can be interpreted better. The results showed that the depth of VT-A and VT-B earthquake spread out at 2 km depth above the sea level of up to 6 km below the sea level and the epicenter spread out in ± 3km radius from the top mountain. Hypocenter position indicates the location of the magma chamber. From the result of the hypocenter distribution relocation, Sinabung have 3 magma chambers in different depth. The most shallow magma chamber and the smallest sixe is at 2 km depth from the summit, the second magma chamber at 6 km depth from the summit and the third magma chamber at 13 km depth from the summit.