Abstract
This paper investigates magnetotelluric (MT) data recorded along a profile in the Sabalan geothermal region, NW of Iran. To find the range of relevant models consistent with the data, this study employed the so-called regularized, tear zone, and sharp boundary inversions. This study could effectively derive three alternative classes of models. Although the models show stable common resistive and conductive features there are some inconsistent details. Unaltered surface rocks and porous Basalt exhibit a high resistive overburden underlain by relatively more conductive Paleozoic sediments. A common signature of hydrothermal systems appears, and resistivities increase beneath a highly conductive clay cap in deeper parts. An intriguing feature resolved in the smoothest inversion model is a second deep conductor of 30 Ωm resistivities at a depth of 3 km, extending close to the surface. It can be related to the hot, solidified volcanic intrusions, resemblingthe heat source in a geothermal system. This study applied the two other inversion approaches for further hypothesis tests. Although the tear zone inversion re-establish the deep conductor (with 38 Ωm resistivities at 3 km depth), it is absent in the sharp boundary inversion result. This study concludes that the second deep conductor has a limited structure resolution.
Highlights
The MT sounding is widely used for geophysical exploration in geothermal fields [1, 2], and the MT data inversion mainly provides its interpretation
Smith et al, (1999) and deGroot-Hedlin and Constable (2004) suggested sharp boundary inversion where a different model parameterization that allows for blocky structures is used
In the sharp boundary inversion, a different model discritization approach is used and 2D earth model is presented by laterally variable layers whose resistivities are described at a set of nodes [6,7]
Summary
The MT sounding is widely used for geophysical exploration in geothermal fields [1, 2], and the MT data inversion mainly provides its interpretation. Smith et al, (1999) and deGroot-Hedlin and Constable (2004) suggested sharp boundary inversion where a different model parameterization that allows for blocky structures is used. In this method the model space is divided into different regions; tear zones where the model norm is minimized independently ([8, 9])
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