Earthquakes: The 1700 Cascadia Mega-Thrust Quake
An earthquake of magnitude 9 rocked the Pacific Northwest on January 26, 1700 around 9:00 PM. A series of independent discoveries over the past two decades have narrowed the window of occurrence of this "great quake" to a precise time. Preliminary evidence consistant with this date came from carbon dating, tree ring studies, and soil deposits. Although these lines of evidence enabled scientists to verify that a great subduction zone earthquake struck the Pacific Northwest within one or two decades of 1700, the exact date date remained unknown.