3D SEISMIC TOMOGRAPHY FOR DETERMINING STRUCTURE Vp, Vs, AND Vp / Vs RATIO IN WESTERN JAVA USING ARRIVAL TIME DETERMINED BY WAVEFORM CROSS-CORRELATION

• Main Author: DWI SASONGKO NIM: 12314023, AGUS
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/25135
• Institution: Institut Teknologi Bandung

<p align="justify">Indonesia is located at the meeting of three major plates which causes Indonesia to have complex geological conditions. Western Java is located in the middle of the Sunda Arc., this region is an active tectonic zone where there is an oblique subduction meeting under Sumatra and normal subduction along the Southern Java. One of the events that can be caused by tectonic activity in this area is an earthquake that can cause loss of life and damage to property both locally and regionally. For this reason, it is necessary to have knowledge and understanding of the characteristics and conditions of tectonic areas that have high seismic activity. Seismic analysis and seismic wave tomography methods can be applied to help understand tectonic activity and image subsurface structures in western Java. In this study, we used arrival time tomography to determine the structure of Vp, Vs and Vp / Vs ratio in western Java. We used earthquake data recorded by the Meteorology, Climatology, Geophysics Agency (BMKG) network which spread from South Sumatra to Central Java. We used 1097 earthquake events recorded by 32 stations from April 2009 to June 2016 with arrival times of 13,755 phase P and 4,831 S phase. The arrival time data for P and S waves were corrected by cross-correlation techniques to obtain accurate arrival times. The results of the tomography with SIMULPS provide an image of the velocity structure under the western part of Java, especially on the volcanic arc that passes through Mount Anak Krakatau, Mount Salak and the mountain complex south of West Java. Low Vp anomalies, low Vs and high Vp / Vs indicate the presence of heat material derived from subducted plate activity that forms volcanic pathways in West Java to South Sumatra.<p align="justify">