The Philippines has six producing geothermal fields with an aggregate capacity of 1,909 MWe and the country is, consistently, the world's second largest power producer from geothermal next to the United States. Aside from these fields, our country boasts of untapped geothermal resources awaiting exploration and development. Initial geological and geochemical studies of the prospects were conducted with the recently concluded inventory of Philippine thermal areas.

Further studies of the prospects are planned with the Controlled Source Magnetotelluric (CSMT) geophysical equipment acquired through the Equipment Donation Program of Japan. The equipment setup proved convenient for rugged terrain typical of the Philippine topography. Test surveys were made in Manito Lowland, Albay and Mabini, Batangas geothermal areas. The first survey identified problems with the equipment but the second survey gathered more meaningful data. CSMT technique aims to characterize the resistivity structure at depth to identify the heat source and outflow regions of a geothermal system. Compared to natural magnetotellurics, the CSMT is cost-effective since it employs direct and steady current source and covers a large area in less time.