Los Angeles ? Just 50 miles off the Pacific Northwest coast is an earthquake hotspot that threatens to unleash on Seattle, Portland and Vancouver the kind of damage that has shattered Chile.

The fault has been dormant for more than 300 years, but when it awakens — tomorrow or decades from now — the consequences could be devastating.

Recent computer simulations of a hypothetical magnitude-9 quake found that shaking could last 2 to 5 minutes — strong enough to potentially cause poorly constructed buildings from British Columbia to Northern California to collapse and severely damage highways and bridges.

Such a quake would also send powerful tsunami waves rushing to shore in minutes. While big cities such as Portland and Seattle would be protected from severe flooding, low-lying seaside communities may not be as lucky.

The Pacific Northwest “has a long geological history of doing exactly what happened in Chile,” said Brian Atwater, a geologist with the U.S. Geological Survey and University of Washington. “It’s not a matter of if but when the next one will happen.”

The last one hit in 1700, a magnitude-9 that sent 30- to 40-foot-tall tsunami waves crashing onto the coast and racing across the Pacific, damaging Japanese coastal villages.

There’s an 80 percent chance the southern end of the fault off southern Oregon and Northern California would break in the next 50 years and produce a megaquake, according to Chris Goldfinger, who heads the Active Tectonics and Seafloor Mapping Laboratory at Oregon State University.

Research presented last year at a seismology conference found that Seattle high-rises built before 1994, when stricter building codes took effect, were at high risk of collapse during a superquake.

Chile and the Pacific Northwest are part of several seismic hotspots around the globe where plates of the Earth’s crust grind and dive. These so-called subduction zones give rise to mountain ranges, ocean trenches and volcanic arcs, but also spawn the largest quakes on the planet.

The magnitude-8.8 Chile quake occurred in an offshore region that was under increased stress caused by a 1960 magnitude-9.5 quake — the largest recorded in history, according to geologist Jian Lin of the Woods Hole Oceanographic Institution.

The temblor destroyed or badly damaged 500,000 homes and killed more than 700 people.

Similar tectonic forces are at play off the Pacific Northwest, where the Juan de Fuca plate is diving beneath North America. At some point, centuries of pent-up stress in the Cascadia subduction zone will cause the plates to slip. Scientists cannot predict exactly when a quake will occur, only that one will happen.