| Date | 28 February 2001 |
|---|---|
| Magnitude | 6.8 Mw |
| Depth | 52 kilometres (32 mi) |
| Countries or regions | Canada |
| Casualties | 1 dead and about 400 injuries |
The Nisqually earthquake was an intraslab earthquake, occurring at 10:54 a.m. PST (18:54 UTC). on February 28, 2001, and was one of the largest recorded earthquakes in Washington state history. The quake measured 6.8 on the MMS 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 miles east in Pasco, Washington. There were also reports that it was felt as far away as Sandpoint, Idaho and Spokane, Washington.[1]
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 stress-related heart condition at the time of the earthquake.[2]
Contents |
One person died from a heart attack and 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.[3][4] 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 also damaged the Alaskan Way Viaduct that runs along the Seattle waterfront and cracked the dome atop the capitol building in Olympia.[2] Additionally, the earthquake caused power outages in downtown Seattle.[5] The U.S. Military's Ft. Lewis & McChord Airforce Bases received slight damage in the quake. There was also very slight damage in Victoria, British Columbia.[6]
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.[7][8]
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 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), and April 13, 1949 (magnitude 7.1, depth 53 km).
|
|||||