Geophysical Studies on Diwak and Derekan Hot Springs

Abstract

Geothermal activity is considerable in the Diwak and Derekan hot spring, Bergas Subdistrict, Semarang Regency, Central Java, Indonesia. Diwak hot spring is located at the Lutung riverside and Derekan at the Klampok riverside. Each of the main geothermal activities is used for tourists area proposes. The geological and shallow subsurface geophysical studies were carried out. Electrical surveys are conducted by 1D and 3D methods on the different sites to clarify the structure and shallow water aquifer. Alluvial well depth measurements have been conducted to predict the flow of shallow aquifer water. We also conducted CO2 emissions and heat flow through soil surrounding the prospect areas to provide a suitable method for mapping out thermally active ground. A description is given of hydrothermal manifestations in the area according to electrical data, CO2 emission and shallow temperature anomaly. The geological structures of study area are summarized according to electrical data and CO2 gas emission. The water level distribution could be interpreted that the shallow aquifer was flow from the western and southern part toward the geothermal spring. The evidence of high temperature anomaly shows that the heat source possibly at southern part of the geothermal hot springs.