PEMODELAN DATA MAGNETOTELLURIK DI LAPANGAN PANASBUMI ROOSEVELT HOT SPRINGS (RHS), UTAH

Abstract

This study discusses the effect of parameter analysis on the data modeling of the magnetotelluric (MT) method in the geothermal field. The parameter in question is the MT curve parameter, which consists of a phase tensor, polar diagram, and tipper (induction arrow) in order to be able to delineate the subsurface structure of the geothermal area based on the rock resistivity value. The result of the parameter analysis of the MT curve is the change in resistivity as a function of frequency or depth, the use of data from the frequency limit in order to obtain representative modeling results for subsurface conditions, the direction of the geoelectrical strike, and the distribution of the conductive layer laterally. The data used in this study consisted of 71 MT measurement points distributed in the Roosevelt Hot Springs (RHS) geothermal field area. The tipper distribution in the 200 Hz–10 Hz frequency range shows a conductive zone that is relatively close to the surface. The 1-D and 2-D dimensionality limits are in the 200 Hz–10 Hz frequency range. This can be seen from the change in the value of the impedance tensor on the polar diagram. The 1D and 2D inversion models can portray good subsurface conditions where the two results show a contrasting resistivity value between sediment layers (basin fill) close to the surface and granitoid formations at greater depths, where the sediment layer has a conductive layer thickness of ±1km, which tends to thicken to the west. High resistivity at large depths is interpreted as heat activity that is still ongoing in the RHS geothermal system.