Subsurface Characterization of the Leyte Geothermal Field, Philippines Using Magnetotellurics (MT)

Abstract

A geophysical study using magnetotellurics (MT) was conducted on Leyte Geothermal Field (LGF) in the Central Philippines. A set of 93 new MT soundings were added to the 298 existing MT data from the LGF. Induction vector analysis indicates that the geoelectric strike in the area is controlled by the left lateral Philippine Fault. The resistivity structure throughout LGF is characterized by a resistive first layer (more the 50 ohm-m), underlain by a conductive second layer (less than 10 ohm-m) followed by a moderately resistive third layer (10-50 ohm-m). 2D inversion of the MT data reveals a high-low-high resistivity signature typical of geothermal systems in volcanic arc setting. Subsurface information such as temperature and alteration data from drilled wells, coincide with the observed resistivity structure. Generated isoresistivity maps and models reveal that multiple resistive dome shaped structures associated with the proven geothermal reservoir, are situated and centered beneath the Plio-Pleistocene volcanic peaks within the LGF. Furthermore, the updoming structures are found to be aligned with the north-northwest oriented mountain range.