The University of Texas logo
Thermal Structure of the Costa Rica Margin along the Middle America Trench

UTIG Seminars

Thermal Structure of the Costa Rica Margin along the Middle America Trench

Robert N. Harris
College of Oceanic and Atmospheric Sciences
Oregon State University


Friday, February 19, 2010, 3:30 p.m. to 4:30 p.m.


Seminar Conference Room, 10100 Burnet Road, Bldg 196-ROC, Austin, Texas 78758


Lawrence Lawver, UTIG

The thermal structure of continental margins provides critical information related to the geodynamics associated with active plate margins. We are integrating multichannel seismic data showing bottom simulating reflectors (BSRs), in-situ thermal data, data from ODP cores, and numerical models of subduction to estimate the thermal structure along the Middle America Trench of Costa Rica. Seismic reflection data from two cruises SO81 and BGR99 show that BSRs are widespread between the lower slope and shelf edge. These BSRs are used to estimate geothermal gradients along the margin. These estimates are calibrated against in-situ thermal data collocated with BSRs in seismic images. Thermal conductivity data comes from both in-situ measurements and needle probe measurements on ODP cores. Comparisons between in situ and BSR derived values of heat flow are good and improve landward with distance from the deformation front likely reflecting the influence of fluid flow at the trench. Heat flow values across the margin generally decrease landward consistent with subduction. Along the margin heat flow increases from north to south but at a rate greater than can be accounted for with simple age dependent cooling models. Additional heat flow data seaward of the trench is being used to initialize thermal models of subduction. Estimates of the thermal structure of the margin are coupled to a conduction-advection thermal model of subduction. The effects of hydrothermal circulation in the subducting upper oceanic crust using a Nusselt number approximation are explored. These models are used to investigate estimated temperatures along the subduction thrust.