Aftershock Mechanism Analysist of An Earthquake in Pidie Jaya Aceh December 7th, 2016

• Main Author: AKBAR RUSLI (NIM : 12313073), KHAIRUL
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/22807
• Institution: Institut Teknologi Bandung

Sumatra Island is one of the islands in Indonesia which has high intensity tectonic activity. This is not separated from the tectonic activity of the Sumatra fault. The active Sumatera fault is caused by the subduction zone activity between the Ocean plate and the Indo-Australian plate. The existence of collisions between these plates causes frequent tectonic earthquakes in the region of Sumatra. On 7th of December 2016, an earthquake with magnitude of 6.5 occurred in Pidie Jaya district, Aceh. The Meteorological, Climatology and Geophysics Agency (BMKG) said that the main earthquake occurred at 5:03:36 am at latitude 5.25° and longitude 96.24°. More than 100 aftershock earthquakes after the main earthquake. A week after the accident, ITB in cooperation with Unsyiah, BMKG and GFZ Potsdam installed 9 seismometers to monitor seismic activity in Pidie Jaya Aceh area. There are 329 afterschock events recorded within a month starting from December 14th, 2016 to January 15th, 2017. In this research we performs (i) hypocenter relocation of the aftershock event using double-difference method, (ii) determinating the moment magnitude value (Mw) of the aftershock with spectral fitting method, and (iii) determining the focal mechanism using moment tensor inversion method. The result of hypocenter relocation shows the existence of a structure oriented strike northwest-southeast direction which is seen from the vertical hypocenter distribution on the A-A' cross section. The magnitude value of the earthquake aftershock moment can be categorized as small with an average of 1.72 and a maximum value of 3,069. The existence of a northwest-southeast trending structure is reinforced by the result of a focal mechanism of 10 aftershock earthquakes obtained. Focal mechanism result gicing two possible solution of fault plane with northwest-southeast and northeast-southwest trend. However, in this study,the real fault plane still difficult to determined and need more futrher study to determne the fault plane of the main earthquake sourcein Pidie Jaya, Aceh.