SUBSURFACE STRUCTURE IDENTIFICATION OF LEMBANG FAULT ZONE BASED ON GRAVITY METHOD

• Main Author: Tio Miranda, Debora
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/50406
• Institution: Institut Teknologi Bandung

Earthquakes that usually occur in Indonesia are tectonic earthquakes. Tectonic earthquakes arise because tectonic plates move together, causing fractures. The plates that form these fractures will be locked and one day will release its energy. This active fracture or commonly called faults need to be identified as an initial step to reduce the risks of disaster. This research was conducted in the Lembang Fault zone. Lembang Fault is a famous active fault located in West Java. Gravity method is one of geophysical method that can be used to identify faults. This method uses gravitational acceleration to determine the subsurface structure. Measurements using Gravimeter LaCoste & Romberg G-928. The value of gravity acceleration readings can be influenced by the position of measurement, topographical conditions, the force of the moon and the sun and instrumental drift. The existence of these factors makes the acceleration value must be reduced by various corrections. After the correction is done, then the separation between regional anomalies and residual anomalies will be done. Residual anomaly values obtained in the range of -27.35 mgal to 29.52 mgal. From this residual anomaly value, inversion modelling was carried out in order to obtain the density value below the surface. The density value in the model shows the presence of lake sediment, tuff, sand and breccia. The existence of a significant difference in density indicates the presence of a fault.