Heat flow along the Costa Rica Seismogenesis Project drilling transect; implications for hydrothermal and seismic processes

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doi: 10.1002/2016GC006314
Author(s): Hass, Bridget; Harris, Robert N.
Author Affiliation(s): Primary:
Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 17(6), p.2110-2127. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 71 refs.; illus., incl. 4 tables, sketch map
Summary: Heat flow analysis of the Costa Rica convergent margin is carried out for seven sites drilled during Integrated Ocean Drilling Program (IODP) Expeditions 334 and 344 as part of the Costa Rica Seismogenesis Project (CRISP). These expeditions are designed to better understand erosional subduction zones. Heat flow measurements were made to improve estimates of the thermal structure of this erosive margin and are located on the incoming plate, toe, lower, middle, and upper slopes of the margin. Heat flow values corrected for the effects of seafloor bathymetry and sedimentation are on average 15% higher than uncorrected values and range from approximately 158-200 mW/m2 on the incoming plate to values of approximately 50 mW/m2 on the middle and upper slopes of the margin. These values are consistent with previous estimates of heat flow showing a landward decrease in heat flow consistent with subduction of the Cocos plate. Preferred thermal models of the shallow subduction zone successfully predicting observed values of heat flow incorporate fluid flow within the upper oceanic aquifer have an uppermost permeability of 10-9.5 m2 and a plate boundary effective coefficient of friction of 0.06. These models suggest that temperatures on the subduction thrust reach 100°C at distances between 30 and 35 km landward of the deformation front. The updip limit of seismicity, as defined by aftershocks events of ML 1-4 recorded following the Mw 6.9 Quepos earthquake, occurs at 25 km landward of the deformation front at temperatures cooler than the 100-150°C typically predicted. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 20 Geophysics, Applied; Aquifers; Bathymetry; Boreholes; Central America; Cocos Plate; Costa Rica; Costa Rica Seismogenesis Project; Earthquakes; East Pacific; Expedition 334; Expedition 344; Geophysical methods; Geophysical profiles; Geophysical surveys; Ground water; Heat flow; Hydrothermal conditions; IODP Site U1379; IODP Site U1380; IODP Site U1381; IODP Site U1412; IODP Site U1414; Integrated Ocean Drilling Program; Magnitude; North Pacific; Northeast Pacific; Numerical models; Pacific Ocean; Plate tectonics; Quepos earthquake; Seismic methods; Seismic profiles; Seismicity; Subduction zones; Surveys; Thermal analysis
Coordinates: N080000 N093000 W0830000 W0943000
Record ID: 2017010907
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