ANALYSIS OF AFTERSHOCK HYPOSENTER RELOCATION FROM THE YOGYAKARTA EARTHQUAKE 2006 ON JUNE 21ST TO JUNE 25TH 2006 USING DOUBLE DIFFERENCE METHOD AND THE MAGNITUDE DETERMINATION

• Main Author: Edwins Silalahi, Jarister
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/46815
• Institution: Institut Teknologi Bandung

Yogyakarta earthquake on May 27, 2006 was one of the earthquakes that caused many casualties. Based on the USGS earthquake records, the earthquake occurred at 5:53:58 WIB with epicenter 7.79 o south latitude and 110.44 o east longitude, 10 km depth, and magnitude of 6.3 Mw. In addition to the USGS agency, several other institutions and researchers who have conducted research on the main earthquake sources gave different results. So, it is necessary to determine and relocate the aftershock earthquake hypocenter in order to get a line that illustrates the geometry of the fault. This research will try to find the main cause of the Yogyakarta earthquake by conducting an analysis of the aftershock earthquake that occurred from 21 - 25 June 2006. The research was conducted by determining the arrival time of the P and S waves first. Then, the arrival time data is used to determine the hypocenter location of the aftershocks with the Hypoellipse program which applies the principle of the Geiger method. After that, the events are paired using the Ph2dt program. Then the hypocenter relocation will be conducted with HypoDD which applies the principle of the Double Difference method. In this study, four earthquake clusters were found. The main cluster in this research is southwest - northeast with strike 50o NE and dip 80o. The fault plane of clusters 1 and 2 have alignment with the Opak fault. Allegedly, the faults are part of a graben system. In addition, local magnitude calculations are also performed to see the magnitude trend. The results obtained indicate a decrease in magnitude.