Are there faults near Seattle and Portland?
Yes. Some of these are well known from geologic or geophysical surveys. Examples include the Seattle Fault and the Portland Hills Fault. How often earthquakes occur on these faults is not well known, but they are believed to have the potential to produce damaging earthquakes. • Q: Why does the Pacific Northwest have earthquakes? A: We are located at a convergent continental boundary, where two tectonic plates are colliding. This boundary is called the Cascadia Subduction Zone. It lies offshore and runs from British Columbia to northern California. The two plates are converging at a rate of about M 3-4 cm/year (1-2 inches/year), and the northeast-moving Juan de Fuca Plate is pushing into North America, causing stress to accumulate. Earthquakes are caused by the abrupt release of this slowly accumulated stress. • Q: How often do earthquakes occur in the Pacific Northwest? A: Typically, each year we locate over 1000 earthquakes with magnitude 1.0 or greater in Washington and Oregon. Of th
