Seismic Frequency Resonance for Geothermal Targeting in a Fault-Controlled Reservoir

Seismic Frequency Resonance Exploration (SFRE) was deployed along two 980-m profiles (L1, L2) in the Linyi South sector of the Jiyang Depression to evaluate its capability for delineating targets in a fault-controlled geothermal reservoir. Continuous ambient-noise data were processed using frequency-domain stacking, active–passive spectral matching, and resonance-based apparent-impedance inversion, yielding images to ~ 2 km depth. The sections consistently resolve four stratigraphic units and the southwest-dipping Fault F1; pronounced impedance reductions within the fault damage zone indicate intense fracturing and enhanced permeability. Within the Guantao Formation, SFRE reveals two zones of elevated geothermal prospectivity at intersections with F1, implying structural connectivity with underlying Cambrian–Ordovician carbonates and sustained recharge. On this basis, two borehole locations are proposed—ZK1 (~ 1600 m) and ZK2 (~ 1650 m)—with expected wellhead temperatures of 55–65°C. Cross-line agreement between L1 and L2 demonstrates method robustness under strong cultural noise and complex near-surface conditions. Remaining uncertainties primarily reflect sensitivity to shallow heterogeneity and the current two-dimensional acquisition geometry, which motivate denser profiling and multi-method joint inversion. Overall, the results establish SFRE as a fast, source-free, and noise-resilient approach for prioritizing drilling targets and characterizing reservoir–fault interactions in fault-controlled geothermal systems.