HR: 0800h
AN: T21B-0524    [Abstracts]
TI: Imaging the Subduction Factory Beneath Central America: The TUCAN Broadband Seismic Experiment
AU: * Abers, G A
EM: abers@bu.edu
AF: Department of Earth Sciences Boston University, 685 Commonwealth Av., Boston, MA 02215 United States
AU: Auger, L
EM: lauger@bu.edu
AF: Department of Earth Sciences Boston University, 685 Commonwealth Av., Boston, MA 02215 United States
AU: Syracuse, E
EM: syracuse@bu.edu
AF: Department of Earth Sciences Boston University, 685 Commonwealth Av., Boston, MA 02215 United States
AU: Plank, T
EM: tplank@bu.edu
AF: Department of Earth Sciences Boston University, 685 Commonwealth Av., Boston, MA 02215 United States
AU: Fischer, K M
EM: karen_fischer@brown.edu
AF: Department of Geological Sciences Brown University, 324 Brook St., Providence, RI 02912 United States
AU: Rychert, C
AF: Department of Geological Sciences Brown University, 324 Brook St., Providence, RI 02912 United States
AU: Walker, A
AF: Department of Geological Sciences Brown University, 324 Brook St., Providence, RI 02912 United States
AU: Protti, J
EM: jprotti@una.ac.cr
AF: Observatorio Vulcanological y Seismological de Costa Rica (OVSICORI), Universidad Nacional, Heredia, 000 Costa Rica
AU: Gonzalez Salas, V
EM: vgonzale@una.ac.cr
AF: Observatorio Vulcanological y Seismological de Costa Rica (OVSICORI), Universidad Nacional, Heredia, 000 Costa Rica
AU: Strauch, W
EM: wil.gf@ineter.gob.ni
AF: Instituto Nicaraguense de Estudios Territoriales (INETER), Direcci¢n General de Geof¡sica, Managua, 000 Nicaragua
AU: Perez, P
AF: Instituto Nicaraguense de Estudios Territoriales (INETER), Direcci¢n General de Geof¡sica, Managua, 000 Nicaragua
AB: The subduction factory processes the solids and volatiles entering oceanic trenches, and produces volcanic arcs, deep earthquakes, and long-term modifications to the deep earth. Central America exhibits some of the global extremes in the factory operation: in the Nicaragua volcanic arc, fluxes of geochemical tracers associated with subducting sediment are among the highest on the planet, while in the adjacent Costa Rica arc, many of the same tracers are weak to absent. The factory must be behaving differently at depth over short distances. To understand this behavior, we deployed in July-August 2004 a seismic array termed TUCAN (Tomography Under Costa Rica And Nicaragua), 48 broadband PASSCAL seismographs operating until early 2006, funded by the NSF Margins program. Deployment has been rapid and successful. The array design features dense transects across the two arc segments and sparser along-strike arrays. This design allows for high-resolution imaging of the subducting plate and mantle wedge across the transition from the high-flux regions of central Nicaragua to the low-flux Costa Rica arc and backarc. Velocity and attenuation tomography, together with measurements of anisotropy, provides constraints on the thermal structure and melt pathways within the mantle wedge. Receiver functions, scattered waves and tomography allow both upper and lower-plate structure to be assessed. Initial inspection of these data show marked variations in signal amplitudes and travel times across the arc, as expected for a hot mantle wedge. Both regional and teleseismic signals show the presence of strong secondary phases emerging from the slab in Costa Rica, both from regional and teleseismic signals, indicating the presence of pronounced low-velocity layers associated with subducting crust. Previous work has indicated the low velocity layer beneath Nicaragua is unusually slow by global standards, perhaps indicating high volatile content. These data will allow a comparison with velocities within the Costa Rica slab, to test the notion that the variations in arc geochemistry reflect differences in slab water content.
DE: 8180 Tomography
DE: 8434 Magma migration
DE: 7230 Seismicity and seismotectonics
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 7218 Lithosphere and upper mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting