Fault Plane Estimation Through Hypocentres Distribution of the July-August 2018 Lombok Earthquakes Relocated by using Double Difference Method

Abstract

Indonesia is actually located in collisions between three large plates of Eurasia, Indo-Australia, and Pacific. It causes earthquakes to occur frequently in several regions, one of which occurs sequentially the 5 big shocks in Lombok in period of July-August 2018. There is a Flores thrust fault in the North of the Lombok Island region. The objective of study is determining whether the earthquakes sequence is related to the fault. The study is done through the analysis of relocated 321 of 489 hypocentres of the earthquakes acquired from 13 BMKG stations in July-October 2018. The hypocentres are relocated by using the double-difference method. The events are focused only with magnitude > 3.5 M. The relocation result is validated by the RMS residual histograms with the average value close to 0. The results show that the seismic activity mostly spread in the northern part of the Island of Lombok. The distribution of the epicenter points tends to form a pattern oriented from West to East in the northern region of the island which is thought to be the zone of the faults. The events most likely have not generated and not laid along the Flores Fault.