High resolution seismic tomography of a Strombolian volcanic cone

We determine the 3D velocity structure of the Puy des Goules, a small, 1 km wide, Strombolian volcano that erupted 10 ky ago in central France, through a high resolution seismic survey. One major goal for this experiment was to develop methods to reach a high resolution focused on the plumbing system. This has raised different problems such as: mixing active sources (explosive, vibroseis) with different signal properties; inverting traveltime residuals of the order of 10 ms which requires the corresponding accuracy on the Digital Elevation Model (DEM), source and sensor locations (300 sites) and traveltime computations. The results of the traveltime tomography reveal three main bodies of high velocity embedded within scoria layers. These bodies can be interpreted as the central chimney and two complex feeding zones that compare quite well with the Puy de Lemptegy, a neighboring cone that was quarried and removed, showing its underlying feeding conduits and dykes. These results represent a first step toward our objective that is to determine geological structures related to natural hazards with a high resolution.