HR: 0830h
AN: T31E-0878    [PDF]
TI: Crustal Seismic Investigation of the Southern Rio Grande Rift at the Potrillo Volcanic Field, Southern New Mexico
AU: * Averill, M G
EM: averill@geo.utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, 500 W. University, El Paso, TX 79968 United States
AU: Miller, K C
EM: miller@geo.utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, 500 W. University, El Paso, TX 79968 United States
AU: Harder, S H
EM: harder@geo.utep.edu
AF: Department of Geological Sciences, University of Texas at El Paso, 500 W. University, El Paso, TX 79968 United States
AB: The southern portion of the Rio Grande Rift (SRGR) has undergone a complicated volcanic and tectonic history culminating in the modern extensional environment. Previous geophysical studies, shallow basement exposures, and petrologic investigations of xenolith suites recovered from two Quaternary maars (Kilbourne Hole and Potrillo Maar) and Eocene intrusions in the Potrillo Volcanic Field (PVF), have provided much insight into the structure and crustal evolution of the southern Rio Grande rift. Earlier seismic results indicate distinct thinning of the crust by 4-6 km into the SRGR from both the northern Rio Grande rift and the adjacent Basin and Range province, and a regional Pn velocity of approximately 7.7 km/s. A broad gravity high of 20-30 mGal as well as high heat flow values in the range of 75 to 125 mWm-2 are also associated with the SRGR. In May of 2003, a seismic survey was carried out to investigate the crustal structure of the SRGR and relate it to xenoliths from the PVF. This experiment 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 with the help of volunteers from 6 universities within the US and the United Kingdom. Preliminary results show energy propagation across the entire length of each shot gather as well as several distinct phases. Crossover distance of the Pn phase is at approximately 160 km shooting from west to east while it is at approximately 130 km shooting from east to west suggesting an eastward dipping Moho interface. Near vertical reflection data that straddles the PVF shows complex PmP reflections at approximately 11 s as well as a possible PmS phase at approximately 15 seconds.
UR: http://www.geo.utep.edu/pub/miller/pvfweb
DE: 8109 Continental tectonics--extensional (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting