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Here's a summary of what's going on above..... The North American plate is moving westward and the Juan de Fuca Plate is moving eastward. These two plates are colliding along the Cascadia Subduction Zone. The Juan de Fuca Plate is diving under the North American Plate (purple arrows at the Subduction Zone fault). But, it doesn't do this gradually on a daily basis. The two plates are somewhat stuck together. This causes the North American Plate to bow upwards in western Washington (picture shoving a flat sheet of paper along a table and against a wall). When the two plates do slip along the subduction zone boundary this bulge in western Washington will flatten out and move west a bit over the Juan de Fuca Plate - causing one HECK of an earthquake and tsunamis in Pudget Sound. It won't be pretty! The last time this happened was in 1700. It is estimated by geologists that the Cascadia Subduction Zone 'slips' like this once every 500 years. Specific timing of earthquakes is very hard to do. We know where it will happen, just not exactly when. |
