Magnetotelluric investigation for imaging the subsurface geoelectrical feature of the prospective Sembalun-Propok geothermal zone, Indonesia

Abstract

This paper discussed the investigation of the Sembalun-Propok geothermal system, West Nusa Tenggara Province, Indonesia. We analyzed the magnetotelluric data and its implication to the subsurface structure related to the system of Sembalun-Propok geothermal reservoir. In this study, information on the dimensionality of regional conductivity structure and its regional strike were analyzed by applying the magnetotelluric phase tensor. By using induction arrows analysis, the influences of the sea toward the magnetotelluric data were also observed. The results show that it could be performing the 2-D modeling for the higher frequency (≥ 1 Hz) magnetotelluric data. The 2-D inversion modeling suggests that the potential geothermal zone is situated in the western-southern part of the study area. In addition, it also can reveal the depth of the unaltered layer (ρ ≥ 500 Ωm). It is probably related to the volcanic rocks in the study area, and its depth is about 0–500 m from the surface. Then, underlying the unaltered layer possibly corresponds to the cap rock layer (ρ = 1–10 Ωm) of the system of the geothermal reservoir.