Analysis of the mentawai region fault field based on earthquake relocation data using the modified joint hypocenter determination (MJHD) method

Abstract

Tectonic conditions in an area are very important to know, one of them is the Mentawai region. Mentawai is an area prone to earthquake disasters, this is because the Mentawai is located between the subduction zone between the Eurasian Plate and the Indo-Australian Plate. One of the earthquake parameters that is needed in analyzing tectonic conditions is the hypocenter. Accurate hypocenter determination can be done by relocating earthquakes using the Modified Joint Hypocenter Determination (MJHD) method. The MJHD method is carried out by inversion of the main earthquake and aftershocks with correction of the station at the earthquake event. The earthquake data in this study began on September 1, 2017, until December 31, 2018, with 1 main earthquake and 104 aftershocks in the format of arrival time. The main earthquake before the relocation is at longitude coordinates 99.85o latitude -2.6o with a depth of 12 km. After being relocated it is at coordinates 99.5413o latitude 2.5779o with a depth of 29 km. The results after the relocation were identified were fault fields occurring in the B-B cross-section ‘nodal plane 2 with a strike of 141o 66o slip 92o. Earthquake relocation using the Modified Joint Hypocenter Determination (MJHD) shows a change in the Root Mean Square (RMS) value <1. This suggests that the earthquake hypocenter after relocation using the Modified Joint Hypocenter Determination (MJHD) method is more accurate.