HR: 15:25h
AN: T43C-08    [Abstracts]
TI: Results From the TICO-CAVA Land Seismic Refraction Survey
AU: Bullock, A D
EM: adb@uwyo.edu
AF: University of Wyoming, Dept. Geology and Geophysics, 1000 E. University Ave, Laramie, WY 82071, United States
AU: * Holbrook, W S
EM: steveh@uwyo.edu
AF: University of Wyoming, Dept. Geology and Geophysics, 1000 E. University Ave, Laramie, WY 82071, United States
AU: Lizarralde, D
EM: dlizarralde@whoi.edu
AF: Woods Hole Oceanographic Institution, Geology and Geophysics, Woods Hole, MA 02543, United States
AU: Van Avendonk, H
EM: harm@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 10100 Burnet Road, Austin, TX 78758, United States
AU: Mora, M M
EM: mmmora@geologia.ucr.ac.cr
AF: Universidad de Costa Rica, Escuela Centroamericana de Geología, San Pedro de Montes de Oca, San Jose, 214- 2060, Costa Rica
AU: Harder, S
EM: harder@geo.utep.edu
AF: University of Texas, El Paso, Department of Geological Sciences, 500 West University Boulevard, El Paso, TX 79968, United States
AU: Alvarado, G
EM: galvaradoi@ice.go.cr
AF: Sismología y Vulcanología, Instituto Costarricense de Electricidad (ICE), 100032-1000, San Jose, CRI 100032-100,
AB: Project TICO-CAVA (Transects to Investigate the Crustal Origin of the Central American Volcanic Arc) is a key part of the MARGINS Subduction Factory initiative to quantify, characterize, and understand the volcanic crust produced in Costa Rica by seismically imaging its volume, extent, seismic properties, and lateral variability. From this information we hope to estimate the major-element composition of the arc crust and draw inferences about the processes controlling volcanic output of the subduction factory in Central America. We will do this with two intimately linked seismic surveys, an onshore explosion refraction survey (2005), and an onshore-offshore airgun survey (2008). Here we present results from Phase I of the project, an onshore explosion seismic refraction survey of the volcanic arc and look forward to phase II, a large onshore-offshore seismic survey in both the Atlantic and Pacific oceans. We acquired seismic refraction/wide-angle reflection data on two lines. Line 1 is 154 km long from the Pacific Ocean to the Caribbean Sea in central Costa Rica, intersecting the main volcanic arc at Volcán Barva. Line 2 is 280 km long and spans the entire length of the active arc in Costa Rica, from north of Volcán OrosÃÆ'­ near the Nicaraguan border, to south of Volcán IrazÃÆ'º. 748 seismometers were deployed on each transect, resulting in a ~200 m receiver spacing on Line 1 and ~370 m spacing on Line 2. Data quality ranges from fair to excellent. Data on the cross-arc line (Line 1) show upper-crustal refractions that can be tracked from coast to coast and, at the longest offsets, deep reflections that may be Moho reflections. Sediments on the Atlantic coastal plain (2-3 km/s) are about 1.5 km thick; beneath this and beneath the volcanic arc is a low-velocity carapace of volcanic material (3-5 km/s) that is 2-4 km thick. Beneath the low-velocity velocities reach 6.0-6.4 km/s at 5-10 km depth. Deeper structure will become better resolved as analysis continues and the onshore-offshore data are collected. The along-arc line (Line 2) shows evidence for distinctly different crustal structure beneath the Guanacaste volcanos and the Cordillera Central. In addition, low-velocity zones that may represent magma chambers exist beneath Poás volcano and between Irazu and Turrialba volcanoes.
DE: 8104 Continental margins: convergent
DE: 8108 Continental tectonics: compressional
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8178 Tectonics and magmatism
DE: 8185 Volcanic arcs
SC: Tectonophysics [T]
MN: 2007 Fall Meeting