At 9:46:23 PM Pacific Time on March 10, 2011 (05:46:23 UTC on March 11), a magnitude 9.0 earthquake occurred 129 km (80 miles) off the coast of Sendai, a city in Honshu, Japan. The earthquake triggered a catastrophic tsunami that produced a wave height of at least 7.3 m (24 ft), which propagated throughout the entire Pacific Ocean basin. Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys positioned around the Pacific Ocean provided real-time data of the impending tsunami as it travelled across the ocean towards the US West Coast. For example, DART buoy 21418 located 833 km (517 miles) NE of Tokyo in 5.68 km of water depth, recorded a 2 m wave. This system provided warning of the tsunami within a half hour after the earthquake.

Because of this warning, coastal communities in Washington and Oregon were evacuated by the time the tsunami hit the US West Coast almost 9 hours after the earthquake occurred. Harbors along the Oregon coast, including Depoe Bay, Coos Bay, and Brookings, and in Crescent City, CA have reported damage to docks and boats in the harbor. Much of the damage was caused by the massive amount of water that was surging in and out of the harbors very quickly.

For more details about the earthquake and the impact of the tsunami in Japan and the Pacific Northwest, please see the OR Dept. of Geology and Mineral Industry's (DOGAMI) Winter 2012 newsletter, Cascadia - The 2011 Japan Earthquake and Tsunami: Lessons for the Oregon Coast