Nisqually earthquake
Encyclopedia
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 (10.6 mi) northeast of Olympia
. The focus was at a depth of 52 km (32.3 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.
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.
Most of the property damage occurred very near the epicenter or in unreinforced concrete
or masonry
building
s, 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 also damaged the Alaskan Way Viaduct
that runs along the Seattle waterfront and cracked the dome
atop the capitol building
in Olympia. Additionally, the earthquake caused power outages in downtown Seattle. 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.
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.
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).
Intraplate earthquake
An intraplate earthquake is an earthquake that occurs in the interior of a tectonic plate, whereas an interplate earthquake is one that occurs at a plate boundary....
earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
, occurring at 10:54 a.m. PST
Pacific Time Zone
The Pacific Time Zone observes standard time by subtracting eight hours from Coordinated Universal Time . The clock time in this zone is based on the mean solar time of the 120th meridian west of the Greenwich Observatory. During daylight saving time, its time offset is UTC-7.In the United States...
(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
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
and lasted approximately 45 seconds. The epicenter
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
of the earthquake was Anderson Island, about 17 km (10.6 mi) northeast of Olympia
Olympia, Washington
Olympia is the capital city of the U.S. state of Washington and the county seat of Thurston County. It was incorporated on January 28, 1859. The population was 46,478 at the 2010 census...
. The focus was at a depth of 52 km (32.3 mi). Tremors were felt as far away as Scio, Oregon
Scio, Oregon
Scio is a city in Linn County, Oregon, United States. The population was 838 at the 2010 census.-Geography:According to the United States Census Bureau, the city has a total area of , all of it land.-History:...
, across the border in Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...
, British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, and 175 miles east in Pasco
Pasco, Washington
Pasco is a city in and the county seat of Franklin County, Washington, United States.Pasco is one of three cities that make up the Tri-Cities region of the state of Washington...
, Washington. There were also reports that it was felt as far away as Sandpoint, Idaho
Sandpoint, Idaho
Sandpoint is the largest city in, and the county seat of, Bonner County, Idaho, United States. Its population was 7,365 at the 2010 census.Sandpoint's major economic contributors include forest products and light manufacturing, tourism and recreation and government services...
and Spokane, Washington.
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
Stress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...
-related heart condition at the time of the earthquake.
Damage and effects
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
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
or masonry
Masonry
Masonry is the building of structures from individual units laid in and bound together by mortar; the term masonry can also refer to the units themselves. The common materials of masonry construction are brick, stone, marble, granite, travertine, limestone; concrete block, glass block, stucco, and...
building
Building
In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...
s, such as those in the First Hill, Pioneer Square
Pioneer Square, Seattle, Washington
Pioneer Square is a neighborhood in the southwest corner of Downtown Seattle, Washington, USA. It was once the heart of the city: Seattle's founders settled there in 1852, following a brief six-month settlement at Alki Point on the far side of Elliott Bay. The early structures in the neighborhood...
and Sodo
SoDo, Seattle, Washington
SoDo is a neighborhood in Seattle, Washington, that makes up part of the city's Industrial District. It is bounded on the north by South King Street, beyond which is Pioneer Square; on the south by South Spokane Street, beyond which is more of the Industrial District; on the west by the Duwamish...
neighborhoods of Seattle. The air traffic control tower
Control tower
A control tower, or more specifically an Air Traffic Control Tower , is the name of the airport building from which the air traffic control unit controls the movement of aircraft on and around the airport. Control towers are also used to control the traffic for other forms of transportation such...
at Sea-Tac Airport
Seattle-Tacoma International Airport
The Seattle–Tacoma International Airport , also known as Sea–Tac Airport or Sea–Tac , is an American airport located in SeaTac, Washington, at the intersections of State Routes 99 and 509 and 518, about west of Interstate 5...
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
Alaskan Way Viaduct
The Alaskan Way Viaduct, completed on April 4, 1953, is a double-decked elevated section of State Route 99 that runs along the Elliott Bay waterfront in Seattle's Industrial District and downtown Seattle. It is the smaller of the two major north–south traffic corridors through Seattle ,...
that runs along the Seattle waterfront and cracked the dome
Dome
A dome is a structural element of architecture that resembles the hollow upper half of a sphere. Dome structures made of various materials have a long architectural lineage extending into prehistory....
atop the capitol building
Washington State Capitol
The Washington State Capitol or Legislative Building in Olympia is the home of the government of the state of Washington. It contains chambers for the Washington State Legislature and offices for the governor, lieutenant governor, secretary of state and treasurer and is part of a campus consisting...
in Olympia. Additionally, the earthquake caused power outages in downtown Seattle. 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.
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
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
'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.
Geological origins
The Puget SoundPuget Sound
Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...
area where this earthquake occurred is prone to deep earthquakes due to the Juan de Fuca
Juan de Fuca Plate
The Juan de Fuca Plate, named after the explorer of the same name, is a tectonic plate, generated from the Juan de Fuca Ridge, and subducting under the northerly portion of the western side of the North American Plate at the Cascadia subduction zone...
tectonic plate's subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
under the North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
as part of the Cascadia subduction zone
Cascadia subduction zone
The Cascadia subduction zone is a subduction zone, a type of convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a very long sloping fault that separates the Juan de Fuca and North America plates.New ocean floor is being created offshore of...
, which causes stress
Stress (physics)
In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...
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).
See also
- List of earthquakes in the United States
- Geology of the Pacific NorthwestGeology of the Pacific NorthwestThe geology of the Pacific Northwest refers to the study of the composition , structure, physical properties and the processes that shape the Pacific Northwest region of the United States and Canada...