Earthquakes in Portland

Portland lies in a high-risk seismic region driven chiefly by the Cascadia Subduction Zone offshore, capable of magnitude-9 megathrust earthquakes that would shake the entire Pacific Northwest for minutes and generate a coastal tsunami. Closer to home, the Portland Hills Fault and other crustal faults run directly through and beneath the metropolitan area, so the city faces both distant megathrust shaking and the possibility of a nearer, shallower quake.

The last great Cascadia rupture struck in January 1700, and geological records show these megathrust events recur every few hundred years on average, making another overdue in geologic terms. Portland's building stock includes many older unreinforced masonry structures, and stretches of the city built on soft river sediments are prone to liquefaction. While the region has not felt a catastrophic quake in modern history, seismologists regard a major Cascadia event as one of the most serious natural hazards facing Oregon.