RELOCATION AND FOCAL MECHANISM ANALYSIS ON MICROEARTHQUAKES IN “IRC” GEOTHERMAL FIELD USING MOMENT TENSOR INVERSION

• Main Author: Rayhan Caesario, Irfandy
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43942
• Institution: Institut Teknologi Bandung

“IRC” Geothermal Field is one of actively producing field in Indonesia. This field is one of the most productive geothermal field in Indonesia, with a capacity of 227 MW, around 16% of national electricity. Fluid movements in a geothermal field can cause microearthquakes. These microearthquakes activities must be monitored because they can give valuable information about on-going explorations, and fluid activities below. The data used in this research are waveforms which were recorded in eleven stations from January to November 2016. To acquire accurate information, the hypocenters must be located precisely. The process of locating hypocenters starts with identifying the P-wave and S-wave and picking the travel times. After that, Geiger method is used to locate initial hypocenters of the microearthquakes, using Geiger’s Adaptive Damping (GAD) software. To determine the clusters, a maximum distance of 3 kilometers in one cluster is used. From GAD result, it can be seen that there are two clusters, one in the north and one in the south. Hypocenters relocation process is used with hypoDD software to increase the hypocenters’ accuracy. From total of 700 events, only 318 events that are relocated. The result shows a better lineation than the initial hypocenters, especially the cluster in the south part. Moment tensor inversion result shows that the mechanism in southern cluster is dominated by sinistral strike slip fault, while the mechanism in northern cluster is dominated by CLVD, caused by fluid activities that associated with reservoir below.