REGIONAL KINEMATIC ANALYSIS OF THE YAKIMA FOLD AND THRUST BELT, WASHINGTON

The Yakima Fold and Thrust Belt (YFTB) in central Washington state is a set of seismogenic thrust/ reverse faults and associated folds roughly aligned with the Olympic-Wallowa Lineament (OWL). Understanding sub-surface fault geometry is directly linked to assessing earthquake potential, as earthquake magnitude scales with fault surface area. We test whether the surface fold geometries of the YFTB can be modeled by either (a) shallowly- dipping listric thrust faults with high surface area; or (b) steep, curviplanar reverse faults with a low surface area. Kinematic models to test these end-member hypotheses are created using published geologic and seismic data. Surface data was compiled in ArcGIS to analyze deformation of Columbia River Basalt flows (CRBs) to interpret the underlying fault geometries within the brittle crust. CRB contacts were digitized to create contoured structure surfaces. These surfaces were combined with outcrop and orientation data and used in 2-D MOVE to produce line-length balanced cross-section interpretations of fault geometries at depth. Data collection and synthesis is underway and results will be presented at the 2017 Cordilleran Section Meeting.