RELOKASI HIPOSENTER GEMPA LOMBOK 17 MARET 2019 MENGGUNAKAN METODE DOUBLE DIFFERENCE

Abstract

Lombok Island, Nusa Tenggara Barat is one of the region in Indonesia which has several large earthquakes history. It is commonly caused by two plate activities, there are subduction in the southern and Flores back arc thrust in the northern island. However, the earthquake that occurred on March 17th, 2019 in Lombok island with 5.4 magnitudes and depth at 18 km identified as an earthquake caused by an unusual source. It is the local normal fault of Gunung Rinjani which had been identified yet. Hypocenter relocation will be needed to obtain more accurate hypocenter that is required to analyze seismicity, tectonic condition, velocity structure, or fault zone. The hypocenter relocation method used in this study is the double-difference method which takes advantage travel time of earthquake pairs toward the stations. Damping value test and several velocity models also used to find more proper results of hypocenter relocation. The best results obtained using damping value 40 and PREM 1-D velocity model being analyzed and validated based on its frequency of residual values. This study shows that the main event caused by the normal fault which has strike 117o in the East-West direction and dip 24o from North to South.