On November 30, 2018, at 8:29 a.m. AKST (17:29 UTC), a

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

7.1 earthquake hit

Anchorage Anchorage, officially the Municipality of Anchorage, is the most populous city in the U.S. state of Alaska. With a population of 291,247 at the 2020 census, it contains nearly 40 percent of the state's population. The Anchorage metropolita ...

Southcentral Alaska Southcentral Alaska (), also known as the Gulf Coast Region,Alaska Department of Commerce, Community, and Economic Development, Northern Opportunity Alaska's Economic Development Strategy, 2016, at 84 (Alaska 2016). Accessed June 1, 2023. https: ...

. The earthquake's epicenter was near Point Mackenzie, about north of

, and occurred at a depth of . It was followed six minutes later by a magnitude 5.7 aftershock centered north-northwest of the municipality. The earthquake could be felt as far away as Fairbanks. The

National Tsunami Warning Center The National Tsunami Warning Center (NTWC) is one of two tsunami warning centers in the United States, covering all coastal regions of the United States and Canada, except Hawaii, Guam, the Northern Mariana Islands, Puerto Rico and the U.S. Virgin ...

—itself located inside the quake zone, in

Palmer, Alaska Palmer is a city in and the county seat, borough seat of the Matanuska-Susitna Borough, Alaska, United States, located northeast of Anchorage on the Glenn Highway in the Matanuska-Susitna Valley, Matanuska Valley. It is the List of cities in A ...

, northeast of Anchorage—issued

tsunami warning A tsunami warning system (TWS) is used to detect tsunamis in advance and issue the warnings to prevent loss of life and damage to property. It is made up of two equally important components: a network of sensors to detect tsunamis and a communic ...

s for nearby coastal areas, including

Cook Inlet Cook Inlet (; Sugpiaq language, Sugpiaq: ''Cungaaciq'') stretches from the Gulf of Alaska to Anchorage, Alaska, Anchorage in south-central Alaska. Cook Inlet branches into the Knik Arm and Turnagain Arm at its northern end, almost surrounding ...

and the

Kenai Peninsula The Kenai Peninsula ( Dena'ina: ''Yaghenen'') is a large peninsula jutting from the coast of Southcentral Alaska. The name Kenai (, ) is derived from the word "Kenaitze" or "Kenaitze Indian Tribe", the name of the Native Athabascan Alaskan tribe ...

, but they were lifted shortly after.

Tectonic setting

Southern Alaska lies at the eastern end of the

Aleutian Trench The Aleutian Trench (or Aleutian Trough) is an oceanic trench along a convergent plate boundary which runs along the southern coastline of Alaska and the Aleutian islands. The trench extends for from a triple junction in the west with the Ula ...

, where the Pacific plate is

subducting Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second pla ...

beneath the North American plate. Near Anchorage, the plates are converging at a rate of 57 mm per year. The region has experienced severe earthquakes in the past, including several

megathrust earthquake Megathrust earthquakes occur at convergent plate boundaries, where one tectonic plate is forced underneath another. The earthquakes are caused by slip along the thrust fault that forms the contact between the two plates. These interplate earthq ...

s. The 1964 earthquake, with a magnitude of 9.2, was the largest earthquake in American history and the second largest to ever be recorded anywhere in the world. Though earthquakes are common in Alaska, they often occur out at sea. This earthquake is more similar to the 2001 Nisqually earthquake located near

Tacoma Tacoma ( ) is the county seat of Pierce County, Washington, United States. A port city, it is situated along Washington's Puget Sound, southwest of Seattle, southwest of Bellevue, northeast of the state capital, Olympia, northwest of Mount ...

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

, than to the 1964 megathrust earthquake.

Earthquake

The earthquake had a magnitude of 7.1 on the

moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mwg, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. was defined in a 1979 paper ...

using a centroid moment tensor inversion of the W-phase. The

focal mechanism The focal mechanism of an earthquake describes the Fault (geology)#Slip.2C heave.2C throw, deformation in the Hypocenter, source region that generates the seismic waves. In the case of a Fault (geology), fault-related event, it refers to the ori ...

shows that the earthquake was a result of normal faulting. A fault dipping at 29° towards the east gives the best match to the observed seismic waveforms. The depth and mechanism are consistent with faulting within the down-going Pacific plate. This implies that the earthquake was an intraslab earthquake within that plate, rather than at the plate boundary between the Pacific and North American plates beneath the Anchorage area. This is a different mechanism than megathrust faults in the region, which do occur on the plate boundary itself. This faulting in the Pacific plate is caused by downward bending while the plate is being forced under Alaska.

Aftershocks

Over 80 aftershocks of various magnitudes were recorded throughout the day, with at least three having magnitudes greater than 5.0. By December 3, 170 aftershocks with a magnitude over 3.0 had been noted. Two more aftershocks hit on February 6, the first with a magnitude of 4.1, and the second coming 23 minutes later with a magnitude of 3.7. Aftershocks were expected to continue for around 300 days after the mainshock.

Damage

Severe damage to several buildings and a highway overpass near

Ted Stevens Anchorage International Airport Ted Stevens Anchorage International Airport is a major airport in the U.S. state of Alaska, located southwest of downtown Anchorage. The airport is named for Ted Stevens, who served as a senator of Alaska from 1968 to 2009. It is included in ...

was reported. There were no fatalities, but at least 117 people were injured, mostly for minor injuries such as cuts, bruises or anxiety. Some suffered broken bones, and one resident suffered serious smoke inhalation while trying to put out a post-quake fire at his home. The

Kenai Peninsula Borough School District The Kenai Peninsula Borough School District (KPBSD) serves 29 communities and served 8,400 from 2021-2022 in the Kenai Peninsula Borough. The district is headquartered in the borough seat of Soldotna, Alaska, Soldotna, and the current Superinten ...

reported that all students were safe. Landings at three airports were temporarily affected by the earthquake: the Ted Stevens International Airport, Merrill Field Airport and

Joint Base Elmendorf–Richardson Joint Base Elmendorf–Richardson is a United States military facility in Anchorage, Alaska. It is a joint base formed from the United States Air Force's Elmendorf Air Force Base and the United States Army's Fort Richardson, which were merged ...

. The

Anchorage Police Department The Anchorage Police Department (APD) is the Police, police department serving the Anchorage, Alaska, Municipality of Anchorage in Alaska. APD is responsible for police services for the entirety of the Municipality of Anchorage, including the c ...

reported major infrastructure damage across the city.

Liquefaction In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of t ...

was reported. Several

traffic light Traffic lights, traffic signals, or stoplights – also known as robots in South Africa, Zambia, and Namibia – are signaling devices positioned at intersection (road), road intersections, pedestrian crossings, and other locations in order t ...

s were knocked down, bringing traffic to a halt. Many roads were also damaged. The

Glenn Highway The Glenn Highway (part of Alaska Route 1) is a highway in the U.S. state of Alaska, extending from Anchorage near Merrill Field to Glennallen on the Richardson Highway. The Tok Cut-Off is often considered part of the Glenn Highway, for a ...

was damaged to the point where officials stated it would likely take a long time to repair. A ramp connecting

Minnesota Drive The Minnesota Drive Expressway is a south–north controlled-access highway, expressway located in the city of Anchorage, Alaska, Anchorage, Alaska, United States. The expressway includes a small portion of O'Malley Road, which is also built t ...

to area streets collapsed, as well as the surrounding hillside. A driver in an SUV who was on the section of destroyed highway was stranded, but uninjured. The

Alaska Railroad The Alaska Railroad is a Class II railroad that operates freight and passenger trains in the state of Alaska. The railroad's mainline runs between Seward, Alaska, Seward on the southern coast and Fairbanks, Alaska, Fairbanks, near the center of ...

had to suspend all operations due to severe damage at their operations center and unknown condition of tracks. The operators of the

Trans-Alaska Pipeline The Trans-Alaska Pipeline System (TAPS) is an oil transportation system spanning Alaska, including the trans-Alaska crude-oil pipeline, 12 pump stations, several hundred miles of feeder pipelines, and the Valdez Marine Terminal. TAPS is one o ...

shut the system down as a precaution; however, they reported that there was no known damage to the pipeline and it later resumed service. Quake damage Glenn Highway Palmer

The

Alaska Airlines Center The Alaska Airlines Center is a 5,000-seat multi-purpose arena in Anchorage, Alaska. It is located on the campus of the University of Alaska Anchorage (UAA) and adjacent to Providence Alaska Medical Center (PAMC). History The arena went through ...

, a large sports complex on the

University of Alaska Anchorage The University of Alaska Anchorage (UAA) is a public university in Anchorage, Alaska, United States. UAA also administers four community campuses spread across Southcentral Alaska: Kenai Peninsula College, Kodiak College, Matanuska–Susitna C ...

(UAA) campus, flooded due to broken fire sprinkler pipes. Several trophy cases were also damaged. UAA's older Wells Fargo Sports Complex suffered similar damage. Over 120 schools in the

and the

Matanuska-Susitna Borough School District Matanuska-Susitna Borough School District (MSBSD) is a school district based in the city of Palmer, Alaska, Palmer, Alaska. It serves 40 schools across Matanuska-Susitna Borough, Alaska, Mat-Su Borough, which each enroll from 15 to 1300 students ...

s were damaged. Eagle River Elementary and Gruening Middle schools in Anchorage, and Houston Middle School in the Mat-Su were the only three to experience severe structural damage. Students in both districts were sent home and schools were closed to assess the damage. Within the three weeks of the earthquake, all schools with the exception of Eagle River Elementary and Gruening Middle schools in Anchorage and Houston Middle School, had re-opened. The remaining three had all experienced severe structural damage and were closed for the rest of the year. Houston Middle School students were sent to attend Houston High School and, in September 2020, the Houston Middle school building was ordered demolished due to a combination of earthquake damage and poor-quality construction. Sixteen students and twelve staff were injured in the quakes districts, including eleven students at MSBSD's Colony Middle School. Injuries were mostly minor. One student had a concussion due to falling books and one teacher went into labor. The newsroom studio of

KTVA KTVA (channel 11) is a television station in Anchorage, Alaska, United States. It is a satellite of PBS member station KAKM (channel 7) which is owned by Alaska Public Media. KTVA's transmitter is located in Spenard—covering the Anchorage ...

in Anchorage (then affiliated with

CBS CBS Broadcasting Inc., commonly shortened to CBS (an abbreviation of its original name, Columbia Broadcasting System), is an American commercial broadcast television and radio network serving as the flagship property of the CBS Entertainme ...

) was heavily damaged, but the channel remained on the air. Several branches in the Anchorage Public Library system sustained damage. Many books were knocked off the shelves, which took days to clean up. Structural damage was noted in some locations. In the Anchorage community of Eagle River, at least one home collapsed during the earthquake. One man in the home, whose spouse was at work, was able to escape with several pets. Significant damage was also done to roads in the Mat-Su. Among the most heavily damaged roads were the Palmer-Wasilla Highway, Pittman Road, Point MacKenzie Road and Vine Road. Suffering the worst damage was Vine Road, a section of which buckled and became impassable. In addition, Matanuska Electric Association reported that 46,000 customers were left without electricity immediately after the earthquake. Overall, damage in Anchorage was estimated to be at least US$30 million, including $10 million to repair pipes, and $10 million in public facilities. Damage estimates to the

Anchorage School District The Anchorage School District (ASD) manages all public schools within the Municipality of Anchorage in the U.S. state of Alaska. It is the 107th largest school district A school district is a special-purpose district that operates local p ...

ranged from $25 to $50 million.

Response

A federal disaster was declared shortly after the earthquake and the

Federal Emergency Management Agency The Federal Emergency Management Agency (FEMA) is an agency of the United States Department of Homeland Security (DHS), initially created under President Jimmy Carter by Presidential Reorganization Plan No. 3 of 1978 and implemented by two Exec ...

(FEMA) deployed personnel from the state

emergency operations center An emergency operations center (EOC) is a central command and control "coordination structure" responsible for managing emergency response, emergency preparedness, emergency management, and disaster management functions at a strategic level dur ...

at Joint Base Elmendorf-Richardson to conduct relief operations. Alaska Governor

Bill Walker Bill Walker may refer to: Australian rules football * Bill A. Walker (1886–1934), Australian rules footballer for Essendon * Bill Walker (Australian footballer, born 1883) (1883–1971), Australian rules footballer for Fitzroy * Bill J. V. Walke ...

said "It's been a 7.2 earthquake, but our response was a 10." Anchorage Mayor

Ethan Berkowitz Ethan Avram Berkowitz (born February 4, 1962) is an American attorney, businessman, and politician from Alaska. From 1997 to 2007 he was the Alaska State Representative for District 26, serving as the Democratic Party Minority Leader from 199 ...

likewise declared a state of emergency for his city, and requested both state and federal assistance. The local public bus system,

People Mover A people mover or automated people mover (APM) is a type of small-scale automated guideway transit system. The term is generally used only to describe systems serving relatively small areas such as airports, downtown districts or theme parks ...

, ended service for the day following the earthquake. The city announced that regular bus service would resume the following day, and would be free of charge for the two days following the earthquake to help city residents get around on damaged roads. The

Alaska Department of Transportation and Public Facilities The Alaska Department of Transportation & Public Facilities (Alaska DOT&PF) is a department within the government of Alaska. Its headquarters are in Alaska's capital city, Juneau. The mission of Alaska DOT&PF is to "''Keep Alaska Moving through ...

moved quickly to inspect bridges and begin road repairs. Although roads in Anchorage aren't normally paved during winter, area asphalt plants were restarted and within days sufficient repairs were made to reopen several heavily damaged roads.

References

External links

*
Event page
from the

IRIS Consortium IRIS (Incorporated Research Institutions for Seismology) was a university research consortium dedicated to exploring the Earth's interior through the collection and distribution of seismographic data. It operated the U.S. National Science Foundati ...

{{DEFAULTSORT:Anchorage earthquake, 2018 2018 earthquakes 2018 in Alaska Earthquakes in Alaska November 2018 in the United States 2018 disasters in the United States History of Anchorage, Alaska