HR: 0830h
AN: S41D-0109    [PDF]
TI: Surface Wave Group Velocity Tomography and Lithospheric S-velocity Structure of South American Continent
AU: * Feng, M
EM: mei@iag.usp.br
AF: Department of Geophysics, IAG, University of Sao Paulo, Rua do Matao, 1226, Cidade Universitaria, Sao Paulo, SP 05508-090 Brazil
AU: Assumpcao, M
EM: marcelo@iag.usp.br
AF: Department of Geophysics, IAG, University of Sao Paulo, Rua do Matao, 1226, Cidade Universitaria, Sao Paulo, SP 05508-090 Brazil
AU: Van Der Lee, S
EM: suzan@tomo.ig.erdw.ethz.ch
AF: Institut fur Geophysik, ETH Honggerberg (HPP), Zurich, CH-8093 Switzerland
AB: A new group velocity tomography is presented for the South American continent including additional stations deployed in the northern and northeastern part of the continent, which had not been covered by previous works. More than 10,000 seismograms were examined with paths principally propagating across the continent of South America. 4000 Rayleigh- and 2270 Love-wave dispersion curves with good quality were retrieved in the period range of 10-150s for Rayleigh wave and 20-70s for Love wave. Single-station group velocities were determined using multiple filtering techniques. 2D group velocity tomography was applied to fundamental-mode Rayleigh and Love waves on a regular geographical grid using a conjugate gradient method. Checkerboard tests showed that our data set permits a lateral resolution of about 300km in the central part of the continent with denser paths coverage. Regionalized dispersion curves have been then inverted for 1D S-velocity profiles inside each block, which have been used to construct the final 3D S-velocity model. Both the 2D group velocity and the 3D S-velocity maps showed good correlation with the major geological provinces like cratons, Andean range, shields and sedimentary basins etc. The lowest velocities are found in the Andean region and the highest velocities in the Amazon craton. The two flat subduction slabs in the western coast of South America were well resolved. Our 3D shear-wave velocity model not only showed general similarity to the results from Partitioned Waveform Inversion and body-wave travel-time tomography, but also improved the resolution in the northern and northeastern part of the continent not covered by previous works.
DE: 7200 SEISMOLOGY
DE: 7218 Lithosphere and upper mantle
DE: 7255 Surface waves and free oscillations
DE: 8180 Tomography
SC: Seismology [S]
MN: 2003 Fall Meeting