Preliminary 2.5D geothermal distribution in Kepahiang region deduced by inversion magnetotelluric (MT) data

摘要

Kepahiang area is one region that has potential in geothermal sources, which are characterized by several manifestations in the form of fumaroles and hot springs. Previous research using magnetotelluric (MT) method shows that geothermal resource was located relatively closed from the source of Kaba Volcano so that it is very hard and risky to explore. Therefore, further research on investigating geothermal resources viewed through 2.5 dimensions (2.5D) is needed. In order to obtain MT data, the MT ADU-07e tool with magnetic and electrical sensors was used at 10 sites observation such us: L-1, L-2, L-3, L-4, A1, A2, A3, A4, A5, and A6 sites respectively. The MT data were recorded in three sampling frequencies, namely 4096 Hz, 1024 Hz, and 128 Hz respectively. The time-series MT data were processed Mapros software to obtain the Edi files, and they were inverted by using ZondMT2D software. Two 2D section models were combined to obtain a 2,5D model. The geothermal distribution result was detected at L-4, A6, and A5, which has a high resistivity value of ～200 ohm-m at 200-2000 m of depth. From these results, it shows that geothermal in the Kepahiang region is originally come from the Bukit Kaba volcano source and distributed to the eastern part (geothermal manifestation). In general, geothermal systems in the Kepahiang region showed the consistency of geothermal systems obtained by volcanic systems due to fractures as a result of the Sumatra Fault Zone (SFZ) movement. Further investigation is needed by adding more MT stations in order to increase model resolution. A high-resolution image of the earth subsurface resistivity plays a key role in the better understanding source of geothermal prospect in Kepahiang region.