Using a time lapse microgravity model for mapping seawater intrusion around Semarang

Abstract

A modeling of time-lapse microgravity anomaly due to sea water intrusion has been conducted. It used field data of aquifer cross section, aquifer thickness and lithology of research area. Those data were then processed using Grav3D and Surfer. Modeling results indicated that the intrusion of sea water resulting in a time-lapse microgravity anomalies of 0.12 to 0.18 mGal, at soil layer density of 0.15g/cm3 to 0.3g/cm3 and at depth of 30 to 100m. These imply that the areas experiencing seawater intrusion were Tanjung Mas, SPBE Bandarharjo, Brass, Old Market Boom and Johar as the microgravity measured there were in the range of 0.12 to 0.18 mGal and the density contrast were at 0.15g/cm3 to 0.28g/cm3. Areas that experienced fluid reduction were Puri Anjasmoro, Kenconowungu and Puspowarno with microgravity changes from-0.06 mGal to-0.18 mGal.