Mapping Geothermal Fluids Using Seismic Absorption and Scattering: A Case Study from Aluto Volcano

Seismic attenuation tomography is used to map fluids and fractures beneath the Aluto volcano geothermal field of the Main Ethiopian Rift. We present 3D models of peak delay ($\Delta \log_{10}(T_{pd})$) and inverse coda quality factor ($Q_c^{-1}$) which are proxies for seismic scattering and absorption. High $Q_c^{-1}$ anomalies are observed near productive geothermal wells with high-temperature gradients and in areas of hydrothermal activity. High scattering attenuation anomalies are spatially associated with faults and fractures that serve as pathways for fluid flow. These variations correlate well with production variations in boreholes across the geothermal field. Furthermore, a prominent high-scattering (low-absorption) anomaly is observed at a depth of approximately 0-3 km bsl beneath Aluto, which is interpreted as the signature of an intrusive igneous body. Together, these methods for measuring seismic attenuation serve as valuable tools in geothermal exploration, offering constraints on fluid distribution, as well as structural and lithological variations.