ANALYSIS OF SUBSURFACE STRUCTURE USING GRAVITY DATA IN STUDYING THE PRESENCE OF FAULTS IN THE CIANJUR AREA, WEST JAVA

• Main Author: Teja Krisna Devana, Made
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86256
• Institution: Institut Teknologi Bandung

There was an earthquake in Cianjur on November 21, 2022 that caused many losses. The initial suspicion was that the earthquake was caused by the activity of the Cimandiri Fault of the Rajamandala segment that passes through Cianjur. However, the results of studies conducted by several researchers related to this earthquake concluded that there were indications of new faults that had not been previously identified. One of the geophysical methods that can be used to describe the subsurface structure is the gravity method. By analyzing the gravity anomaly response obtained, it is expected to provide an overview of the subsurface structure of Cianjur. The data used in this study are combined gravity data between data measured directly by the author and data measured by the survey team from BRIN (Badan Riset dan Inovasi Nasional). From the processing and analysis that has been done, a complete Bouguer anomaly map is obtained which shows an anomaly value range between 46,5-59,5 mGal, a regional anomaly map with a value between 48,5-57 mGal, and a residual anomaly map with a value range between (-2)-2,8 mGal. There is a alignment and an area of interest in the center shown by the residual anomaly, tilt derivative, and total horinzal of tilt derivative maps. The alignment is thought to be related to the contact boundary of the rock unit, and the interesting area in the center of the map is thought to be related to the intrusion in the subsurface. From the model that has been made, there are 5 main rock units that make up Qyg (breccia and volcanic mudflow of Mount Gede), Qyc (basalt boulders), Qot (breccia and lava from the oldest volcano), Pb (breccia, lava, hard tuffaceous sandstone), and Ha (intrusion of hornblende andesite and hornblende diorite porphyrites). In the model, there is a fault that is thought to be formed due to intrusion movement in the center of the model. The existence of this fault confirms the indication of a new fault that has not been identified as concluded by several previous geophysical studies.