Shear-wave Velocity Structure around Teide Volcano: Results Using Microtremors with the SPAC Method and Implications for Interpretation of Geodetic Results

Deformation analysis and simulation of volcanic edifices require the construction of models of elastic properties of those structures. In this paper we present an analysis of microtremor measurements recorded during the performance tests of two temporary seismic arrays installed in the eastern portion of the Teide caldera in 1994. We take advantage of recent developments of the SPAC method and use spatial cross-correlation computations to estimate phase velocity dispersion of Rayleigh waves at the location of the arrays. We show that the extension of the standard SPAC method is valid in the case of our data, justifying its use and supporting the generalization of the SPAC method to single station pairs. The phase velocity dispersion curve obtained was inverted to recover the shear-wave profile at the site of the arrays. Our results indicate that the subsoil structure of the caldera is laterally homogeneous at the scale of a few km about the location of the arrays. We obtained about 315 m of volcanic sediments overlying rocks with a shear-wave velocity of 2 km/s. These results are robust and are a starting point to further modelling of deformation, permanent or transient, at this volcanic edifice, which can be useful in the interpretation of different observed fields. In fact, the computation of deformations and gravity changes due to possible volcanic intrusions in two models; one considering the volcanic sediments and the other without considering them, provided different results in the near field.