The thermal structure of the lithosphere block overriding a subduction zone is complicated and diverse with surface heat flow values ranging from the highest to the lowest regional values on the earth. The thermal characteristics of the Cascadia subduction zone in the Pacific Northwest of the United States have been extensively studied during the last 15 years, especially as regards the geothermal potential of the Cascade volcanic arc. As a side result of these studies some data has been collected in the low heat flow outer arc block as well. As the primary objective of the project these data will be used to develop a time-dependent three-dimensional temperature model of the subduction zone and the outer arc block. This temperature model will be used as a basis for evaluating the mechanical characteristics of the zone as a way to investigate the potential for large subduction zone type earthquakes and to explore the unique setting of the Cascadia subduction as the reason that no deep focus earthquakes are associated with the zone.
