Bill Fry

A new finite-frequency shear-velocity model of the European-Mediterranean region

[1]xa0We invert a global phase-anomaly database of intermediate- to long-period Rayleigh waves, recently updated with increased coverage in the European-Mediterranean region, on a global scale with a higher resolution parameterization in the region of interest. We first compare phase-velocity inversions based on ray and finite-frequency theory and derive for each a corresponding set of local phase-velocity dispersion curves (one per model pixel) between 35 s to 300 s period. Effects of the two different theories on the three-dimensional upper-mantle structure are investigated by inverting each dispersion curve for radial shear-velocity profiles. The combination of a gradient-descent method and a random-Monte-Carlo model search provides an estimated shear-velocity model with associated uncertainties for depths between 40 km to 400 km. While differences between ray-theoretical and finite-frequency models are small compared to model uncertainty, comparisons with independent models favor the finite-frequency one.

Europe‐Mediterranean tomography: High correlation between new seismic data and independent geophysical observables

[1]xa0To improve the fidelity of European tomographic images, we implement variable resolution parameterization, finite-frequency and ray theory, and improved data coverage in new tomographic inversions. We supplement an existing high-quality database of global teleseismic phase velocity observations of both Love and Rayleigh waves with a set of new phase delay observations recorded by a dense array of stations in the region. We invert these data to find global phase velocity maps, characterized by a more densely parameterized Europe and Mediterranean. We compare our seismic images with laterally variable independent geophysical observables, including crustal thickness, gravity, and heat flow and find correlations between 0.25 and 0.6. While at most periods finite-frequency and ray-theory yield almost coincident results, we find some possibly significant differences in the phase velocity of 150s Rayleigh waves. Our results represent significant progress toward high-resolution modeling of upper mantle S-velocity structure, with the possibility of also constraining seismic anisotropy.