Imaging the crust and the upper mantle of Cumbre Vieja volcano (La Palma, CanaryIslands) through receiver function analysis.

The receiver function analysis (RF) is a commonly used and well-established method to investigate subsurface crustal and upper mantle structures, removing the source, ray-path and instrument signature. RF gives the unique of sharp seismic discontinuities and information about P-wave (P) and shear-wave (S) velocity below a seismic station.

This work aims to study the crust and the upper mantle of La Palma up to 40 km depth by using RF analysis. Because of the geological context as an active island, it is expected that Mohorovičić’s discontinuity has a complex geometry under Cumbre Vieja and possibly a high anisotropy can be present. This makes the application of conventional RF function analysis difficult.

That is why in this study, we applied the frequency-domain RF inversion using multi-taper deconvolution. After that, we have applied the transdimensional approach of Bodin et al. (2012) to determine 1D profiles of P and S wave velocities in terms of probability distributions, as well as the probability of a discontinuity to be located at a given depth. This approach does not require establishing “a priori” the number of layers to be used for the inversion.

Our preliminary results allowed us to correlate the different discontinuities besides the stations we got deployed around Cumbre Vieja. We have seen at least for different layers with a significant change in their Vp/Vs ratios. Moreover, we have determined the Moho topography under Cumbre Vieja and the whole island.

These results are compared with the seismicity observed during the 2021 Cumbre Vieja eruption, mainly located at the base of the crust (10-15 km) and in the upper mantle (20-30 km), possibly indicating the presence of two magmatic reservoirs at these depths.

 

References

Bodin, T., Sambridge, M., Tkalčić, H., Arroucau, P., Gallagher, K., & Rawlinson, N. (2012). Transdimensional inversion of receiver functions and surface wave dispersion. Journal of Geophysical Research: Solid Earth, 117(B2).