Well, now you have a tiny idea of how I look like (this picture was taken on the Milford Track, New Zealand).

Research

In this project, we consider the limitations of regional scale inversion methods. First, a ray theory based tomography was realized for North America using the extensive dataset available. Because of scattering effects, the resolution turned out to be limited. We performed therefore phase velocity tomography for the same region using the Rytov approximation which takes into account off-great circle heterogeneities. Comparison is made between the two sets of phase velocity maps obtained. Later on, the improved phase velocity maps will be inverted for S-wave velocity. At a final stage, we use geoid data to constrain the relation density-velocity in the upper mantle and infer the thermo-chemical structure of the upper mantle beneath the North American continent.

Shear wave velocity model for North America,

We show here a shear wave velocity model of the uppermost mantle beneath the North American plate. The model is obtained by inversion of fundamental mode Rayleigh waves in the period range 40-150 s. A dataset of 7700 phase velocity dispersion curves, displaying good path coverage is used. The three dimensional velocity s tructure down to 250 km is imaged by an inversion procedure based on the great c ircle path approximation. Imaging the complete North American and Caribbean plates is in addition to the u se of an extensive new dataset a significant complement to recent studies. Our m odel displays high resolution in the United States, southern Canada and Central America. The differentiation between Archean craton and tectonic continent is well resolv ed in the model. Relative high velocities (+8%) are imaged beneath the N orth American cratonic shield in Canada and northeastern United States down to 2 50 km. Low velocities anomalies (-7%) characterize the tectonically acti ve western Cordillera, these persist down to 150 km depth, from Alaska to the so uthern border of Mexico. This feature extends in the continent interior to the C olorado Plateau, and correlates well with surface tectonics. High velocities are retrieved beneath Wyoming, agreeing with cratonic surface outcrops. In addition , no distinct anomaly is imaged below the Yellowstone hotspot track. The Iceland hotspot and the Mid Atlantic ridge are associated with low velocities. Along th e United States west coast, no fast anomaly is associated with the Juan de Fuca plate subduction. The Gulf of Mexico and the central part of the Caribbean Sea a re imaged as high velocities down to 150 km.

If you would like to receive the phase velocity models or shear wave velocity models used in this study, in digital form, please send me an email to:

godey@emsc-csem.org

Publications

(3) Godey, S., Trampert, J., Deschamps, F., and Snieder, R., 2004. Thermal and compositional anomalies beneath the North American continent. Journal of Geophysical Research , 109, B01308, doi:10.1029/2002JB002263.

To get a reprint of this publication, contact me by email: godey@emsc-csem.org

(2) Godey, S., Snieder, R., Villasenor, A. and Benz, H., 2003. Surface wave tomography of North America and the Caribbean using global and regional broadband networks: phase velocity maps and limitations of ray theory. Geophysical Journal International, 152 , 3, 620-632.

(1) Godey, S., 2002. Structure of the uppermost mantle beneath North America : Regional surface wave tomography and thermo-chemical interpretation   PhD thesis, Utrecht University.

Presentations

Curriculum Vitae

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