IDENTIFICATION OF ACTIVE FAULTS IN WEST JAVA BASED ON EARTHQUAKE HYPOCENTER DETERMINATION, RELOCATION, AND FOCAL MECHANISM

• Main Author: SUPENDI (NIM:22414301), PEPEN
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/29925
• Institution: Institut Teknologi Bandung

<p align = "justify">West Java region is located in high seismicity and active tectonic setting region influenced by subducting Indo-Australian plate beneath Eurasia plate. There are several on land active faults namely Cimandiri fault, Lembang fault, and Baribis fault in the region. Meteorological, Climatological, and Geophysical Agency (MCGA) earthquake data catalog from 2009 to 2015 shows the earthquakes were located not only around active faults but also relatively far away from the active faults in West Java region. In this study, determine of the earthquake location by Geiger method through re-picking of P-and S-wave arrival time recording by MCGA network. Hypocenter relocation using Double-Difference method and then conducting focal mechanism analysis to estimate the type of fault using moment tensor method. The results indicate better hypocenter, where earthquakes have described patterns of seismicity in West Java. There are several clusters of earthquakes at shallow depths (&#8804; 30 km) which probably related to the Cimandiri fault, Lembang fault, and the Baribis fault. In addition, there are a cluster of earthquakes in southern West Java (Garut earthquake clusters) trending southwest-northeast which possibly related to a local fault in Garut. The presence of seismic activity in this area indicates that have the active faults. The validity through the histogram of travel time residual shows good data processing where the residual value is close to zero. Source mechanism throughout the Lembang fault is a left-lateral fault conform with previous studies, as well as along the Cimandiri fault shows left-lateral fault, but to the southwards shows the thrust fault. While the source mechanisms of the western part of Baribis fault indicates thrust fault, but eastwards shows oblique fault dominant thrust. Beside that in Garut cluster shows right-lateral fault.<p align = "justify">