AIP Conf. Proc. 1554, 218 (2013); doi: 10.1063/1.4820324
Radon and Thoron Analysis of Soil Gas Survey
Case Study of Rajabasa Geothermal Field
Nandi Haerudin1,*, Wahyudi2 and Wiwit Suryanto2
1Department of Geophysics Engineering, Faculty of Engineering, Lampung University,
Jl. Sumantri Brojonegoro No. 1, Bandar Lampung 35145, Indonesia
2Department of Physics Faculty of Mathematics and Natural Sciences, Gadjah Mada University,
Jl. Sekip Utara No. 1,Yogyakarta 55281, Indonesia
Radon and Thoron concentration of soil gas was measured by Scintrex Radon detector RDA 200 in the Rajabasa geothermal field, South Lampung regency, Indonesia. This study is aimed todeterminethe buried fault zoneunder theoverburdenlayer. The survey areacovers three geothermal manifestations in the southern part of Rajabasageothermalfield. The result indicates fault system trending SW-NE (N 60o E) and SSW-NNE (N 8o E). The contour map of Radon concentration performed high value in the three manifestations which was included survey area; those are 123 cpm in Gunung Botak hot spring, 145 cpm in Kunjir fumarole and 382 cpm about 300 m from Bulakan (Way Belerang) fumarole. Three manifestations were connected by two fault. The first fault passed begin from Gunung Botak directed to Kunjir and the other across the first fault from SSW to Bulakan. The contour map of Radon and Thoron ratio indicated that the second fault system is not only indicate the presence of the fault /fracture zones but also
show the extension of the faults/fractures from the depth to the surface.
Keywords: Radon, Thoron, Soil gas survey, Geothermal field.