Tomoves results: A 3D velocity model for earthquake location under the Vesuvius volcano
Anthony Lomax and Jean Virieux
UMR Geosciences Azur, 250 Rue A. Einstein, 06560 Valbonne, France
A. Zollo and P. Capuano
Dipartimento di Scienze Fisiche, Universita' di Napoli, Italy; Observatorio Vesuviano, Naples, Italy
The Vesuvius volcano and its surroundings can be characterised by 3D structural variations and significant topography. There is also large uncertainty in the absolute and relative depth distribution of seismic events under the volcano. Thus, for an improved understanding of the dynamics and risk of Vesuvius, it is important to obtain a 3D velocity model for earthquake location.
We have developed a smooth, 3D, P-wave velocity model for Vesuvius by interpolation of 2D velocity sections obtained from tomographic inversion of the Tomoves active seismic experiment data. We describe the methodology used to construct the 3D model and confirm that predicted travel times in this model agree with arrival time picks for the Tomoves data.
To asses the quality and utilty of interpolated 3D model, we relocate natural seismic events under Vesuvius using this model and a global-search, 3D location method, and compare the solution quality and hypocentre distribution for these 3D locations with those for a representative layered model. We also examine the size and spatial variation of station residuals and their relation to likely 3D velocity variations and to the Vp/Vs ratio, and asses the information gained about event depths and depth uncertainty.