¿Afecta la extensión sin-orogénica a la sismogénesis interplaca en el prisma de acreción de Cascadia (Noroeste de EEUU)?

Resumen

The Cascadia margin is an example where extension is found in a convergent scenario, locally affecting the shallower levels (2-3 km) of the slope of the accretionary wedge. BSR-derived heatflow determined from pre-stack depth-migrated seismic sections decreases in areas thinned by listric normal faults. This heat-flow decrease added to the thinning of the overriding plate produced by extension results in lower temperatures at the subduction thrust plane in the area where otherwise the brittle-ductile transition would take place. We suggest extension contributes to the cooling of the plate's interface by two processes: 1) by reducing the thickness of the overriding plate and 2) by promoting fluid circulation and advective heat transfer at the depths reached by the listric normal faults, above which, lower heat-flow rates are observed. This refrigeration of the plate's interface under extended areas produces a landward migration of the brittle-plastic transition, widening the seismogenic zone and driving it closer to the shore.