Understanding Geothermal Structures beneath Corbetti

Seismic imaging of active volcanic systems provides essential constraints on crustal structure and magmatic processes. In this study, we investigate the Corbetti caldera, located in the Central Main Ethiopian Rift (CMER), using both ambient seismic noise and earthquake body waves recorded by two temporary seismic array deployments. Array beamforming and cross-correlation techniques are applied to continuous noise records to explore the potential to extract stable noise directions and Green’s functions suitable for surface-wave analysis; the observed noise field shows seasonal variability likely linked to rainfall. To image the crust, we employ a Bayesian transdimensional Monte Carlo inversion of P- and S-wave arrival times from local earthquakes. The inversion simultaneously resolves three-dimensional velocity perturbations in VP, VS, and their ratio Vp⁄Vs , while quantifying uncertainties through posterior ensembles.
The resulting velocity models highlight shallow low-Vs anomalies in the southern sector of the caldera, consistent with zones of hydrothermal alteration or partial melt, and a narrow low-velocity corridor in the north that may correspond to fluid pathways within the upper crust. These features are robustly constrained by well-sampled rays, whereas deeper anomalies remain less well resolved. Comparison with InSAR- and MT-derived deformation sources further indicates that seismically imaged anomalies are geometrically consistent with regions of active deformation, though causal connections remain to be tested.
Together, our results provide new seismic constraints on the shallow crustal structure beneath Corbetti, demonstrating the complementary use of ambient noise analysis and Bayesian body-wave inversion. These independent approaches highlight the potential of seismic imaging to resolve hydrothermal alteration zones and fluid pathways in rift-related volcanic environments.