HR: 16:20h
AN: S44A-01    [Abstracts]
TI: Upper Mantle Structure of South America from Joint Inversion of Waveforms and Fundamental-mode Group Velocities of Rayleigh Waves
AU: Feng, M
EM: anmeijian@yahoo.com.cn
AF: Inst. of Geomechanics, Chinese Academy of Geological Sciences, Beijing, China
AU: * van der Lee, S
EM: suzan@earth.northwestern.edu
AF: Dept. Earth & Planetary Sci., Northwestern University, Evanston, IL 60208-2150, United States
AU: Assumpcao, M
EM: marcelo@iag.usp.br
AF: Dept. of Geophysics, Univ. of Sao Paulo, Sao Paulo, Brazil
AB: A new tomographic S-wave velocity model for the upper mantle beneath South America is presented. We developed and applied a new method of simultaneously inverting regional S & Rayleigh waveforms and fundamental-mode Rayleigh-wave group velocities, to better constrain upper mantle S-velocity structure and Moho depth. We used about 5700 Rayleigh wave group velocity dispersion curves and 1537 regional wave trains with paths principally passing through the South American continent. The joint inversion of this data set provided a new 3D upper mantle S-velocity model and a Moho depth model for South America, which fits both the group velocity and regional waveform data sets well. New features of the final 3D S-velocity and Moho depth model correlate well with known geotectonic units on a regional scale. The Moho depth ranges from 30 km in the central Chaco basin to 42 km beneath the Amazonian craton and 45-70 km beneath the orogenic Andean belt. The imaged S-velocity indicates an average lithosphere thickness of around 160 km for the Amazonian craton. High velocities are imaged beneath the Amazon and São Francisco cratons and part of the Paraná and Parnaíba basins down to about 150 km. Low to very low velocities are imaged beneath the central Andes and the Chaco, Pantanal and northwestern Paraná basins.
DE: 9360 South America
SC: Seismology [S]
MN: 2007 Joint Assembly