An investigation of the 3D electrical resistivity structure in the Chingshui geothermal area, NE Taiwan

Abstract

The Chingshui geothermal area southwest of the Ilan plain is identified as a western extension of the Okinawa Trough in the northern Taiwan subduction system. Numerous geophysical, geological and geochemical investigations have been conducted since the 1970s by the Industrial Technology Research Institute, the Chinese Petroleum Corporation of Taiwan and the National Science Council of Taiwan. These studies indicated that the Chingshui stream is one of the largest geothermal areas for electricity generation in Taiwan. However, the power generation efficiency has not met initial expectations. Magnetotelluric (MT) data analyses show that the Chingshui geothermal region is a geologically complex area. A full three-dimensional (3D) inversion was therefore applied to reprocess the MT data and provide the detailed electrical structure beneath the Chingshui geothermal region. The 3D geoelectrical model displays an improved image that clearly delineates the Chingshui geothermal system geometry. Two conductive anomalies are imaged that possibly indicate high potential areas for geothermal energy in the Chingshui geothermal system. One of the potential areas is located in the eastern part of the Chingshui Fault at shallow depths. A significant conductive anomaly is associated with high heat flow and fluid content situations southwest of the geothermal manifest area at depth. A higher interconnected fluid indicates that this area contains the highest potential for geothermal energy in the Chingshui geothermal system.