First horizontal derivative and Euler Deconvolution in application for reconstructing structural signature over the Blawan-Ijen Geothermal area

Abstract

A ground gravity survey was conducted over the Blawan-Ijen geothermal area covering about 176 km2 area. A total of 72 stations were measured with 1.0 – 1.5 km spacing. The data obtained were then processed using several corrections for gravity data to get Complete Bouguer Anomaly (CBA). The gravity method was chosen because of the ability to detect geological structures corresponding to the rocks density of the field study. Two types of gravity technique, First Horizontal Derivative (FHD) and Euler Deconvolution (ED), have become widely used to interpret the structure condition. FHD technique delineates a geological boundary of different density body while ED technique estimates a source location and depth of structures. Furthermore, 3-D inversion of magetotelluric data result was also used as a reference to support 2-D gravity forward modeling. The main structure which probably controlled the emergence of Blawan-Ijen hotspring is indicated by maximum FHD value at the northern part area. Moreover, the ED result shows the depth of structures in Blawan-Ijen geothermal area is mostly about 250 – 1000 meters.