High-Resolution Seismic Imaging of Vulcano Island Based on Matrix Imaging

Imaging the subsurface plumbing systems of active volcanoes is essential for understanding magmatic and fluid transport processes and for improving eruption forecasting. However, seismic imaging in volcanic environments is intrinsically challenging due to strong heterogeneities, intense wave scattering, and rapidly evolving geological conditions. These difficulties are often compounded by complex topography and logistical constraints, which limit the deployment of dense seismic networks and reduce the effectiveness of conventional source-based imaging approaches.

In this context, passive techniques exploiting incoherent seismic wavefields, particularly Ambient Noise Tomography (ANT), have become central tools for volcanic imaging. Since its introduction, ANT has enabled the retrieval of inter-station Green’s functions from ambient noise cross-correlations, allowing imaging of subsurface structures without active sources. While early applications focused mainly on shear-wave velocity (Vs) models, recent developments have demonstrated the potential of ambient noise data to constrain additional physical properties, including three-dimensional seismic attenuation.

Building on these advances, a matrix-based imaging framework has recently been introduced to seismology. Matrix Imaging exploits the array response matrix constructed from impulse responses between all receiver pairs, which can be obtained from ambient noise correlations. This approach allows the coherent extraction of scattered and reflected body-wave energy embedded in noise records, without requiring a detailed a priori velocity model, making it particularly well suited for sparse arrays in strongly heterogeneous volcanic settings.

We applied Matrix Imaging to ambient seismic noise data recorded at Vulcano Island (Italy), a volcano characterized by recurrent unrest episodes but no eruptions since 1888–1890. Previous studies suggest a deep magma reservoir at ~20 km depth and a possible shallow storage zone at ~2 km, overlain by an active hydrothermal system. Interpretations of recent unrest, including the 2021 episode, remain debated. This study aims to provide new constraints on the shallow structure of Vulcano Island and to assess the potential of matrix-based methods for high-resolution passive imaging of active volcanic systems.