HR: 1340h
AN: T33A-1348    [Abstracts]
TI: Constraints on Crust and Upper Mantle Velocities Beneath the Gulf of California from the Analysis of Love and Rayleigh waves
AU: * Persaud, P
EM: ppersaud@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AU: Di Luccio, F
EM: diluccio@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome, 00143 Italy
AU: Clayton, R W
EM: clay@gps.caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AB: The Gulf of California is one of only a few newly forming ocean basins where seafloor spreading is still not fully established. Improved knowledge of crustal composition and thickness, and the inferred thermal state of the upper mantle is needed for a more complete understanding of how this plate boundary has evolved. This in turn provides a basis for explaining what role if any past periods of subduction may have played and sheds light on the mechanism by which the apparently slow, but imminent transition to seafloor spreading is manifested in small segmented basins. Whether the crust is mainly oceanic, continental or transistional in composition has broader implications for studies on magmatism, structure and deformation. Furthermore, the constraints provided by reliable crustal velocities on earthquake locations and determinations of crustal thickness via receiver functions are invaluable. Here we present a surface wave dispersion study of regional earthquake data recorded by the NARS-Baja array, a set of 14 broadband seismic stations surrounding the Gulf of California. This study is conducted with both Love and Rayleigh waves, whose dispersion allows their velocities to vary with period and depth of penetration. They thus provide valuable information on crust and upper mantle velocities along their paths. We will use a number of earthquakes to create a 2D map of the phase velocities in the region, which can then be used to determine the 3D structure. Our initial results show noticeable differences in the group velocities of different paths. Due to the fact that the NARS-Baja array straddles the plate boundary, we are able to make additional first order comparisons of the crust on opposite sides of the conjugate margins.
DE: 7218 Lithosphere and upper mantle
DE: 7220 Oceanic crust
DE: 7255 Surface waves and free oscillations
DE: 7205 Continental crust (1242)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting