UTILIZATION OF SATELLITE GRAVITY ANOMALY DATA FOR TWO-DIMENSIONAL MODELING OF SUBSURFACE STRUCTURE OF SLAMET VOLCANO, CENTRAL JAVA, INDONESIA

Abstract

Study using the satellite gravity method has been carried out in the Slamet Volcano area, Central Java, Indonesia. The gravimetric satellite has produced gravity anomalies data which have been corrected up to free air correction. This study purposes to determine the subsurface structure of Slamet Volcano by modeling residual gravity anomalies data. Data processing which has been conducted includes bouguer correction, terrain correction, data reduction to a horizontal surface, separation of regional and residual anomalies data, modeling, and interpretation. The residual gravity anomalies data obtained from the processing range from -40.62 – 66.22 mGal. The anomalies data are modeled in two dimensions (2D) to obtain the subsurface structure model of Slamet Volcano. The 2D-subsurface models on the AB and CD trajectories show the presence of magma chamber and several lava rocks which form the body of the volcano. The rocks are interpreted as andesitic lava with a density value of 2.72 g/cm3, andesitic-basaltic lava with a density value of 2.89 g/cm3, basaltic lava with a density value of 2.97 g/cm3, and magma chamber with a density value of 1.32 g/cm3. Such low value of magma chamber density relative to the surrounding rocks, indicates that Slamet Volcano is still active.