Bottom-simulating reflector variability at the Costa Rica subduction zone and corresponding heat flow model

Author(s): Cavanaugh, S.; Bangs, N. L.; Hornbach, M. J.; McIntosh, K. D.
Author Affiliation(s): Primary:
University of Texas at Austin, Institute for Geophysics, Austin, TX, United States
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: We use 3D seismic reflection data acquired in April - May 2011 by the R/V Marcus G. Langseth to extract heat flow information using the bottom-simulating reflector across the Costa Rica convergent margin. These data are part of the CRISP Project, which will image the Middle America subduction zone in 3D. The survey was conducted in an area approximately 55 x 11 km, to the northwest of the Osa Peninsula, Costa Rica. For the analysis presented here, 3D seismic data were processed with Paradigm Focus software through post-stack time migration. The bottom-simulating reflector (BSR)--a reverse polarity reflection indicating the base of the gas hydrate phase boundary--is imaged very clearly in two regions within the slope-cover sediments in the accretionary prism. In deep water environments, the BSR acts as a temperature gauge revealing subsurface temperatures across the margin. We predict BSR depth using a true 3D diffusive heat flow model combined with IODP drilling data and compare results with actual BSR depth observations to determine anomalies in heat flow. Uniform heat flow in the region should result in a deepening BSR downslope toward the trench, however our initial results indicate the BSR shoals near the trench to its shallowest level below sea floor of approximately 96 m below the sea floor, suggesting elevated heat flow towards the toe. Landward, the BSR deepens to about 333 m below the sea floor indicating lower heat flow. Both BSR segments display a trend of deepening landward from the trench, however the depth below the sea floor is greater overall for the landward segment than the segment near the toe. We suggest two regimes with differing heat flow exist across the margin that likely represent two separate fluid flow regimes - one from recently accreted sediments near the prism toe and the other through the older materials making up the prism.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 20 Geophysics, Applied; Bottom-simulating reflectors; Central America; Costa Rica; East Pacific; Gas hydrates; Geophysical methods; Heat flow; Integrated Ocean Drilling Program; Marine sediments; North Pacific; Northeast Pacific; Pacific Ocean; Sediments; Seismic methods; Spatial variations; Subduction zones
Coordinates: N080000 N111500 W0823000 W0860000
Record ID: 2012049844
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