Application of CSAMT in Urban Mid-deep Geothermal Exploration: A Case Study of the Pyroclastic Rock Area in Changle, Fuzhou

Most urban areas currently face challenges of insufficient geothermal resource exploration, yet demand for mid-deep geothermal energy (typically targeting depths of 1000–3000 m) continues to grow. In practical exploration, methods must balance cost efficiency with high precision while overcoming terrain complexities and strong anthropogenic electromagnetic interference, which puts forward higher requirements for the exploration method. In this paper, Controlled Source Audio-frequency Magnetotelluric Method (CSAMT) is adopted to carry out experimental exploration in the volcanic clastic rock area with complex surface topography and serious interference from anthropogenic activities. The distribution and numerical characteristics of different anomalous low-resistance zones are explored by changing different transmitter positions, transmitter parameters and receiver gains, and the optimal construction parameters are summarized. It is concluded that increasing the transmitter current to 20A can effectively improve the anti-interference capability, and under the condition of rationally choosing the transceiver distance and strengthening the receiver gain, the exploration precision and accuracy can be effectively improved. The improved construction parameters of CSAMT can realize the accurate geothermal exploration in urban areas, which can guide the exploration of middle and deep geothermal resources.