Subsurface Interpretation of the Sembalun Area, East Lombok using the Gravity Method

Abstract

The Sembalun area in UTM coordinates is located atEast hanging 452120,3 to 437998,9 and Northing 9062924 to 9085495 and belongs to the UTM 50S zone which is located on Lombok Island, West Nusa Tenggara. The purpose of this study is to determine the presence of subsurface geological structures in the Sembalun area, East Lombok. The geophysical method used in this research is method gravity namely by finding the distribution of density values and finding values Complete Bouguer Anomaly (CBA) which will be used to perform 2D modeling of subsurface geological structures in the study area using software Grablox. The data used in this research is secondary data in the form of GGMplus 2013 satellite imagery data gravity disturbance and Earth Residual Terrain Model (ERTM2160). The results obtained from this study include the rock density obtained by the parasnis method of 2.815 g/cm3. The fault structure is in the North to Southwest of the study area and there is also a caldera in the middle of the study area (between Sembalun Bumbung and Sembalun Lawang). Manifestations in the form of hot springs are in the south (close to Mount Pusuk). The results of 2D modeling with Grablox are dominant with high density indicating that the study area is dominated by andesitic lava rock.