HR: 0800h
AN: T41E-1274    [Abstracts]
TI: The 2003 Potrillo Volcanic Field Seismic Experiment, Southern Rio Grande Rift: New Refraction Results From a Classic Continental Rift
AU: * Averill, M G
EM: averill@geo.utep.edu
AF: University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79962 United States
AU: Miller, K C
EM: miller@geo.utep.edu
AF: University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79962 United States
AU: Harder, S M
EM: harder@geo.utep.edu
AF: University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79962 United States
AB: The Rio Grande Rift is a major Tertiary tectonic feature that profoundly modifies the lithospheric structure of the southern Rocky Mountains. Patterns of magmatism and extensional structures of the rift both crosscut and reoccupy older structures including those associated with Precambrian continental assembly, late Paleozoic Ancestral Rockies and late Mesozoic to Early Tertiary Laramide tectonism. Modern active source experiments allow us to illuminate the connection between mantle, crustal, and surfaces processes. In May of 2003, the Potrillo Volcanic Field (PVF) experiment was carried out to investigate the crustal structure of the southern Rio Grande Rift and relate it to xenoliths from within PVF. This experiment was comprised of 8 shots of 1000-2000 lbs., 793 seismic recorders (TEXANS) deployed at variable spacing of 100 m, 200m and 600m over 205 km. Near vertical reflection shot data image numerous intracrustal reflections, complex reflectivity at Moho near 11 s, particularly beneath the PVF, and reflected energy due to the conversion of P to S at the Moho. A tomographic velocity model shows a change in mid-crustal velocities from 5.5 - 6 km/s west of the PVF to 6 - 6.5 km/s to its east. The Moho may be as deep as 35 km and likely dips to the east. Here we present a new velocity model from ray-based modeling of secondary arrivals from within the crust and from the crust-mantle boundary, and interpret the model in light of xenolith data.
DE: 8109 Continental tectonics--extensional (0905)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting