Geologically guided ambient noise tomography inversion with 3-D interface structures: methodology and application to a gold mine region in China

SUMMARY Seismic surface wave tomography, particularly when leveraging dense array data, has become a widely used method for investigating shallow subsurface velocity structures. The shallow structures are usually characterized by rapid seismic velocity changes (i.e. seismic interfaces) due to variations in rock properties, sedimentary environments or tectonic features. However, the commonly used grid-based parametrization of the velocity field in surface wave tomography often struggles to accurately constrain such interface geometries. In addition, traditional surface wave inversion methods typically rely on 1-D inversion at individual stations using dispersion curves, followed by interpolation to construct 2-D or 3-D models. This approach can sometimes introduce spurious features and reduce model reliability. To address these limitations, we propose a geological and level-set parametrization approach for surface wave tomography, allowing for the explicit consideration of interface structures in inversion. This method is then combined with the Ensemble Kalman Inversion to optimize subsurface structures. Synthetic tests demonstrate that integrating 3-D interface parametrization in tomography significantly enhances the reliability of the velocity model and the recovery of interface geometries. Applying this approach to the Woxi gold mine region in China yielded inversion results that closely align with existing borehole data. This study highlights the advantages of level-set parametrization for 3-D interface imaging in seismic tomography, underscoring its potential in subsurface mineral exploration.