RUI: Using an Elastic Dislocation Model to Test an Alternative Hypothesis Regarding the Cascadia Subduction Zone

Suny College At Geneseo, Geneseo NY

Investigators

Abstract

Verdonck EAR-0208019 In most models of Cascadia subduction, lithology and heat flow models constrain the downdip extent of coupling between the subducting and overriding plates. Recent seismological studies suggest that some of the previous assumptions made regarding lithology may be unjustified. A preliminary model suggests that active surface deformation can be the result of deep coupling in addition to the shallow region that is indicated by currently accepted models. An exploratory model is being developed that tests the hypothesis that the Cascadia subduction zone is locked deeper than currently thought. Traditional two dimensional dislocation modeling is being employed as a first step, possibly followed by more advanced models. Three seismic hazards pose a threat to western Oregon and Washington state: large megathrust earthquakes; moderate size earthquakes on crustal faults; and large intraplate earthquakes within the subducted slab. All three of these hazards may be influenced by the location and extent of coupling between the subducting Juan de Fuca and overriding North America plates. Reducing the uncertainty regarding the downdip limit of this locked region will allow for better assessment of the potential for damaging earthquakes near the highly populated urban areas of the Pacific Northwest.