Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey
text 3D seismic reflection data were acquired by the R/V Langseth and used to extract heat flow information using bottom-simulating reflector (BSR) depths across the southern Costa Rica convergent margin. These data are part of the CRISP Project, which will seismically image the Middle America subdu...
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ftunivtexas:oai:repositories.lib.utexas.edu:2152/ETD-UT-2012-08-6217 2023-05-15T17:12:13+02:00 Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey Cavanaugh, Shannon Lynn Bangs, Nathan Lawrence Bailey McIntosh, Kirk D. Barnes, Jaime Tatham, Robert 2012-08 application/pdf http://hdl.handle.net/2152/ETD-UT-2012-08-6217 eng eng http://hdl.handle.net/2152/ETD-UT-2012-08-6217 2152/ETD-UT-2012-08-6217 Costa Rica CRISP project Bottom-simulating reflector Heat flow Subduction zone thesis 2012 ftunivtexas 2020-12-23T22:10:33Z text 3D seismic reflection data were acquired by the R/V Langseth and used to extract heat flow information using bottom-simulating reflector (BSR) depths across the southern Costa Rica convergent margin. These data are part of the CRISP Project, which will seismically image the Middle America subduction zone in 3D. The survey was conducted in an area approximately 55x11 km, northwest of the Osa Peninsula, Costa Rica. For the analysis presented here, seismic data were processed using a post-stack time migration. The BSR—a reverse polarity seismic reflection indicating the base of the gas hydrate phase boundary—is imaged clearly within the slope-cover sediments of the margin wedge. If pressure is taken into account, in deep water environments the BSR acts as a temperature gauge revealing subsurface temperatures across the margin. Two heat flow models were used in this analysis. In the Hornbach model BSR depth is predicted using a true 3D diffusive heat flow model combined with Integrated Ocean Drilling Program (IODP) thermal conductivity data and results are compared with actual BSR depth observations to constrain where heat flow anomalies exist. In the second model heat flow values are estimated using the heat flow equation. Uniform heat flow in the region should result in a deeper BSR downslope toward the trench due to higher pressure; however results indicate the BSR is deepest at over 325 meters below the seafloor (mbsf) further landward and shoals near the trench to less than 100 mbsf, suggesting elevated heat flow towards the toe of the accretionary prism. Heat flow values also reflect this relation. In addition to this survey-wide trend, local heat flow anomalies appear in the form of both circular patterns and linear trends extending across the survey, which can be related to mounds, thrust faults, folds, double BSRs, and seafloor erosion imaged in the seismic data. I suggest that these areas of higher local heat flow represent sites where advection of heat from deep, upward-migrating, thermogenically-sourced fluids and/or gases may be taking place. These heat flow trends have implications for not only earthquake nucleation, but also methane hydrate reserve stability. Geological Sciences Thesis Methane hydrate The University of Texas at Austin: Texas ScholarWorks Langseth ENVELOPE(15.668,15.668,68.338,68.338) The Toe ENVELOPE(-59.167,-59.167,-62.333,-62.333) |
institution |
Open Polar |
collection |
The University of Texas at Austin: Texas ScholarWorks |
op_collection_id |
ftunivtexas |
language |
English |
topic |
Costa Rica CRISP project Bottom-simulating reflector Heat flow Subduction zone |
spellingShingle |
Costa Rica CRISP project Bottom-simulating reflector Heat flow Subduction zone Cavanaugh, Shannon Lynn Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey |
topic_facet |
Costa Rica CRISP project Bottom-simulating reflector Heat flow Subduction zone |
description |
text 3D seismic reflection data were acquired by the R/V Langseth and used to extract heat flow information using bottom-simulating reflector (BSR) depths across the southern Costa Rica convergent margin. These data are part of the CRISP Project, which will seismically image the Middle America subduction zone in 3D. The survey was conducted in an area approximately 55x11 km, northwest of the Osa Peninsula, Costa Rica. For the analysis presented here, seismic data were processed using a post-stack time migration. The BSR—a reverse polarity seismic reflection indicating the base of the gas hydrate phase boundary—is imaged clearly within the slope-cover sediments of the margin wedge. If pressure is taken into account, in deep water environments the BSR acts as a temperature gauge revealing subsurface temperatures across the margin. Two heat flow models were used in this analysis. In the Hornbach model BSR depth is predicted using a true 3D diffusive heat flow model combined with Integrated Ocean Drilling Program (IODP) thermal conductivity data and results are compared with actual BSR depth observations to constrain where heat flow anomalies exist. In the second model heat flow values are estimated using the heat flow equation. Uniform heat flow in the region should result in a deeper BSR downslope toward the trench due to higher pressure; however results indicate the BSR is deepest at over 325 meters below the seafloor (mbsf) further landward and shoals near the trench to less than 100 mbsf, suggesting elevated heat flow towards the toe of the accretionary prism. Heat flow values also reflect this relation. In addition to this survey-wide trend, local heat flow anomalies appear in the form of both circular patterns and linear trends extending across the survey, which can be related to mounds, thrust faults, folds, double BSRs, and seafloor erosion imaged in the seismic data. I suggest that these areas of higher local heat flow represent sites where advection of heat from deep, upward-migrating, thermogenically-sourced fluids and/or gases may be taking place. These heat flow trends have implications for not only earthquake nucleation, but also methane hydrate reserve stability. Geological Sciences |
author2 |
Bangs, Nathan Lawrence Bailey McIntosh, Kirk D. Barnes, Jaime Tatham, Robert |
format |
Thesis |
author |
Cavanaugh, Shannon Lynn |
author_facet |
Cavanaugh, Shannon Lynn |
author_sort |
Cavanaugh, Shannon Lynn |
title |
Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey |
title_short |
Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey |
title_full |
Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey |
title_fullStr |
Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey |
title_full_unstemmed |
Heat flow variability at the Costa Rica subduction zone as modeled by bottom-simulating reflector depths imaged in the CRISP 3D seismic survey |
title_sort |
heat flow variability at the costa rica subduction zone as modeled by bottom-simulating reflector depths imaged in the crisp 3d seismic survey |
publishDate |
2012 |
url |
http://hdl.handle.net/2152/ETD-UT-2012-08-6217 |
long_lat |
ENVELOPE(15.668,15.668,68.338,68.338) ENVELOPE(-59.167,-59.167,-62.333,-62.333) |
geographic |
Langseth The Toe |
geographic_facet |
Langseth The Toe |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_relation |
http://hdl.handle.net/2152/ETD-UT-2012-08-6217 2152/ETD-UT-2012-08-6217 |
_version_ |
1766069014800367616 |