Low values of horizontal shortening occur on the OLMT and SFZ west end. There is also significant northeast shortening in the WRZ south of Mt. Rainier. Heat flow jumps to high values in the Oregon Cascades and other anomalies such as the Nevada high, and eastern Snake River high bound a region of generally high heat flow. The lows in the coast ranges and highs in eastern Oregon, northern Nevada, and SW Idaho strongly influence the stress patterns in our models. Shear zones and faults in the western U.S. and Canada are shown as red lines.
White arrows are motion vectors and black arrows are principal stress directions.
The patterns of faults and shear zones illustrate the paths interpreted taken for Pacific-North America interior shear to exit back to the Queen Charlotte transform. The whole of the western U.S. is behaving like a sheared deck of cards with the San Andreas fault and Queen Charlotte faults forming the bottom and top cards. Scale at right is in milligals. The concentration of mafic rocks under Vancouver Island and in the coast ranges of Washington and Oregon cause the most dominant anomalies. Lows in the Olympic Mts.