HR: 12:05h
AN: S41F-08    [PDF]
TI: Mantle Structure Beneath Central South America
AU: * VanDecar, J C
EM: vandecar@dtm.ciw.edu
AF: Carnegie Insitution of Washington, Department of Terrestrial Magnetism 5241 Broad Branch Rd. NW, Washington, DC 20015-1305 United States
AU: Silver, P G
EM: silver@dtm.ciw.edu
AF: Carnegie Insitution of Washington, Department of Terrestrial Magnetism 5241 Broad Branch Rd. NW, Washington, DC 20015-1305 United States
AU: James, D E
EM: james@dtm.ciw.edu
AF: Carnegie Insitution of Washington, Department of Terrestrial Magnetism 5241 Broad Branch Rd. NW, Washington, DC 20015-1305 United States
AU: Assumpcao, M
EM: marcelo@iag.usp.br
AF: University of Sao Paulo, Department of Geophysics Rua do Matao 1226, Sao Paulo, 05508-900 Brazil
AU: Schimmel, M
EM: schimmel@ija.csic.es
AF: University of Sao Paulo, Department of Geophysics Rua do Matao 1226, Sao Paulo, 05508-900 Brazil
AU: Zandt, G
EM: zandt@geo.arizona.edu
AF: University of Arizona, Department of Geosciences Gould-Simpson Building, Tuscon, AZ 85721-0077 United States
AB: Making use of 60 digital broadband seismic stations that have operated across central South America in recent years, we have undertaken an inversion for the upper- and uppermost lower-mantle P- and S-wave velocity structures beneath the region. We have combined data from four portable PASSCAL-type experiments as well as the 3 GTSN permanent stations (LPAZ, BDFB and CPUP) and 1 Geoscope station (SPB) located in the region. The portable data were deployed at various times between 1992 and 1999 and include: 28 sites from the Brazilian Lithosphere Seismic Project (BLSP: Carnegie Institution of Washington and Universidade de Sao Paulo), 16 sites from the Broadband ANdean JOint experiment (BANJO: Carnegie Institution of Washington and University of Arizona), 8 sites from the Seismic Exploration of the Deep Altiplano project (SEDA: Lawrence Livermore National Laboratory) and 4 sites from the University of Brasilia. The P- and S-wave relative delay times are independently obtained via a multi-channel cross correlation of band-passed waveforms for each teleseismic event. These data are then inverted using an iterative, robust, non-linear scheme which parameterizes the 3-D velocity variations as splines under tension constrained at over 120,000 nodes across South America between latitudes of 15 and 30 degrees South. Amongst other features, we robustly image the high-velocity subducting Nazca plate penetrating into the lower mantle and the high-velocity root of the ~3.2 Gyr old Sao Francisco Craton extending to depths of 200-300 km. We will discuss the consistency between our tomographic models and predictions of dynamic mantle models based on plate tectonic reconstructions of subduction.
DE: 7203 Body wave propagation
DE: 7218 Lithosphere and upper mantle
DE: 7260 Theory and modeling
DE: 8102 Continental contractional orogenic belts
DE: 8124 Earth's interior--composition and state (old 8105)
SC: Seismology [S]
MN: 2003 Fall Meeting