2001 Nisqually earthquake
|Date||February 28, 2001|
|Depth||52 kilometers (32 mi)|
|Countries or regions||United States, Canada|
|Casualties||1 dead, about 400 injuries|
The Nisqually earthquake was an intraslab earthquake, occurring at 10:54 am PST (18:54 UTC) on February 28, 2001. One of the largest recorded earthquakes in Washington state history, it measured 6.8 on the moment magnitude scale and lasted approximately 45 seconds. The epicenter of the earthquake was Anderson Island, about 17 km (11 mi) northeast of Olympia. The focus was at a depth of 52 km (32 mi). Tremors were felt as far away as Scio, Oregon, across the border in Vancouver, British Columbia, Canada, and 175 mi (282 km) east in Pasco, Washington. There were also reports that it was felt as far away as Spokane, Washington and Sandpoint, Idaho.
The quake caused some property damage in Seattle and surrounding areas. Although there were no reports of deaths directly from the earthquake, local news outlets reported that there was one death from a heart attack at the time of the earthquake.
Damage and effects 
About 400 people were injured. Most of the property damage occurred very near the epicenter or in unreinforced concrete or masonry buildings, such as those in the First Hill, Pioneer Square and Sodo neighborhoods of Seattle. The air traffic control tower at Sea-Tac Airport was heavily damaged during the quake; it has since been replaced with a more earthquake-resistant tower. The quake splintered a buttress under the dome of the capitol building in Olympia, however previous earthquake-resistance work prevented more serious harm to the building. Additionally, the earthquake caused power outages in downtown Seattle. The U.S. Military's Ft. Lewis and McChord Air Force Base received damage in the quake. There was very slight damage in Victoria, British Columbia.
Following the quake, many buildings and structures in the area were closed temporarily for inspection. This included several bridges, all state offices in Olympia, and Boeing's factories in the Seattle area. Various schools in the state also closed for the day. The Fourth Avenue bridge in downtown Olympia was heavily damaged due to the quake and was later torn down and re-built. In Seattle, the Alaskan Way Viaduct and its seawall were damaged, forcing the viaduct to close for emergency repairs and ultimately factoring into the decision to replace the viaduct entirely.
Geological origins 
The Puget Sound area, where this earthquake occurred, is prone to deep earthquakes due to the Juan de Fuca tectonic plate's subduction under the North American Plate at 3.5 to 4.5 cm. a year as part of the Cascadia subduction zone, which causes stress in the former as it sinks into the mantle. As an intraslab earthquake, it was produced by a change in volume as rock changed from one form to another. Similar significant earthquakes occurred in the same general region on April 29, 1965 (magnitude 6.5, depth 63 km (39 mi)), and April 13, 1949 (magnitude 7.1, depth 53 km (33 mi)).
See also 
|Wikimedia Commons has media related to: 2001 Nisqually earthquake|
- Dewey, James W.; Margaret G. Hopper, David J. Wald, Vincent Quitoriano, and Elisabeth R. Adams (2002). Intensity Distribution and Isoseismal Maps for the Nisqually, Washington, Earthquake of 28 February 2001. U.S. Geological Survey. Retrieved August 15, 2009.
- "A Comparison of the February 28, 2001, Nisqually, Washington, and January 17, 1994, Northridge, California Earthquakes". Southern California Earthquake Center. Retrieved May 16, 2012.
- Susan Wyatt (February 28, 2011). "10th anniversary of Nisqually earthquake". King 5 News. Retrieved May 16, 2012.
- Trinity Parish Church on First Hill was severely damaged in the Nisqually Earthquake of 2001, It was rebuilt, restored and earthquake-retrofitted. This work was completed in 2005.
- Highland, Lynn M. (2002). An Account of Preliminary Landslide Damage and Losses Resulting from the February 28, 2001, Nisqually, Washington, Earthquake. U.S. Geological Survey. Retrieved August 15, 2009.
- David Postman (March 5, 2001). "Capitol did 'remarkably well'". The Seattle Times (seattletimes.nwsource.com). Retrieved 2012-05-16.
- Linn, Allison (February 28, 2001). "Bill Gates speech interrupted by quake". The Associated Press. Retrieved March 30, 2007.
- Earthquakes Canada – Report (2001-02-28). Accessed January 23, 2009.
- "Fourth Avenue bridge: Bridge over rubbled water". The Olympian. 2002. Retrieved July 30, 2008.
- "Quake Capsules-Fourth Avenue Bridge". The Olympian. September 2, 2001. Retrieved July 30, 2008.
- "About the Alaskan Way Viaduct and Seawall". WSDOT. Retrieved May 16, 2012.
- Peter W. McDonough (ed.). The Nisqually, Washington Earthquake of February 28, 2001. Reston, VA: ASCE, TCLEE. ISBN 9780784406151.