INVERSION MODELING OF GRAVITY ANOMALY DATA FOR MAPPING OF SUBSURFACE ROCK DENSITY IN THE PURWOKERTO-PURBALINGGA GROUNDWATER BASIN AREA

Abstract

The utilization of gravimetric satellite data for mapping gravity anomaly on the Earth's surface has been widely used, especially for very large areas, such as groundwater basins. This research purposes to map the density of subsurface rocks in 3D in the Purwokerto-Purbalingga Groundwater Basin area based on the inversion model of the gravity anomalies data. The research stages that have been carried out include data access, bouguer correction, terrain correction, data reduction to a horizontal surface, separation of regional and residual anomalies data, 3D-inversion modeling, and interpretation. Gravity anomalies data have been accessed from the GGMplus 2013 website with a spatial resolution of 220 m. The results of data processing after data separation is residual gravity anomalies data. The anomalies data are distributed at the average topographical elevation of the research area (243.92 m). Inversion modeling of the residual anomalies data has been carried out, in order to obtain a 3D-model of subsurface rock density with values ranging from 1.20 – 4.80 g/cm3. The modeling results show that the Purwokerto-Purbalingga Groundwater discharge area is in the form of a basin filled with alluvial deposits with density values ranging from 2.10 – 2.55 g/cm3 and a depth of more than 4 km.