2011 Oklahoma earthquake
Encyclopedia
The 2011 Oklahoma earthquake was a 5.6 magnitude
intraplate earthquake
which occurred on November 5, 2011, at 10:53 pm CDT (03:53 UTC, November 6, 2011) in the U.S. state
of Oklahoma
. According to the U.S. Geological Survey
(USGS), it was the most powerful earthquake ever recorded in Oklahoma. The previous record was a 5.5 magnitude earthquake that struck near the town of El Reno
in 1952. The quake's epicenter was approximately 44 miles (70.8 km) east-northeast of Oklahoma City
, near the town of Sparks
and was felt in the neighboring states of Texas
, Arkansas
, Kansas
and Missouri
and even as far away as Tennessee
and Wisconsin
. The quake followed several minor quakes earlier in the day, including a 4.7 magnitude foreshock
. The quake had a maximum perceived intensity of VIII on the Mercalli intensity scale
as detected in the town of Prague
. Numerous aftershock
s were detected after the main quake, with a few registering at 4.0 magnitude.
to the western part of Creek County. It is a strike-slip fault, where two adjacent crustal blocks slide horizontally past each other, but unlike the similar moving San Andreas Fault
, the Wilzetta Fault is not located near the margins of any tectonic plates. Earthquake activity in this region has been on the rise since 2008, though there is no indication that a more severe earthquake is imminent. From 1972 to 2008, between 2 to 6 earthquakes were recorded annually by the USGS, however 50 were recorded in 2009. The USGS and the Oklahoma Geological Survey are installing more seismometer
s to better monitor the increased activity. Aftershocks from the 5.6 quake, including some that can be felt, are expected to last for months. The Oklahoma Geological Survey reported that a minor earthquake swarm which occurred in January 2011 could possibly have been due to hydraulic fracturing
, which is a process used to extract oil from oil wells. However, geologists with the USGS and other entities have made it clear that the 5.6 magnitude quake was entirely due to natural causes.
had "buckled
" in three locations and that several nearby homes had major damage and there were also numerous reports of broken windows and other minor damage, mostly to residences. Some local residents reported minor masonry damage and a chimney collapsed at one residence, while a few residents near the epicenter
reported a noise which sounded like thunder in the distance as the earthquake struck. The Oklahoma Department of Emergency Management reported that 2 people suffered minor injuries, 14 homes had various levels of damage, and that Benedictine Hall
at St. Gregory's University
in Shawnee
had one turret collapse and two others damaged, forcing the closure of the building.
(NWS) reported that weather radar
detected insects, bats and birds which had apparently taken flight immediately after the quake. The NWS radar indicated that the tremors were significant enough that those animals that could leave the ground, did so.
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...
intraplate earthquake
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....
which occurred on November 5, 2011, at 10:53 pm CDT (03:53 UTC, November 6, 2011) in the U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
. According to the U.S. Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...
(USGS), it was the most powerful earthquake ever recorded in Oklahoma. The previous record was a 5.5 magnitude earthquake that struck near the town of El Reno
El Reno, Oklahoma
El Reno is a city in Canadian County, Oklahoma, United States, in the central part of the state. A part of the Oklahoma City Metropolitan Statistical Area, El Reno is west of downtown Oklahoma City...
in 1952. The quake's epicenter was approximately 44 miles (70.8 km) east-northeast of Oklahoma City
Oklahoma City, Oklahoma
Oklahoma City is the capital and the largest city in the state of Oklahoma. The county seat of Oklahoma County, the city ranks 31st among United States cities in population. The city's population, from the 2010 census, was 579,999, with a metro-area population of 1,252,987 . In 2010, the Oklahoma...
, near the town of Sparks
Sparks, Oklahoma
Sparks is a town in Lincoln County, Oklahoma, United States. The population was 137 at the 2000 census. The center of population of Oklahoma is located in Sparks .-Geography:Sparks is located at ....
and was felt in the neighboring states of Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
, Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
and Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
and even as far away as Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
and Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
. The quake followed several minor quakes earlier in the day, including a 4.7 magnitude foreshock
Foreshock
A foreshock is an earthquake that occurs before a larger seismic event and is related to it in both time and space. The designation of an earthquake as foreshock, mainshock or aftershock is only possible after the event....
. The quake had a maximum perceived intensity of VIII on the Mercalli intensity scale
Mercalli intensity scale
The Mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude M_w usually reported for an earthquake , which is a measure of the energy released...
as detected in the town of Prague
Prague, Oklahoma
Prague is a city in Lincoln County, Oklahoma, United States. The population was 2,138 at the 2000 census.-Geography:Prague is located at .According to the United States Census Bureau, the city has a total area of , all of it land....
. Numerous aftershock
Aftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...
s were detected after the main quake, with a few registering at 4.0 magnitude.
Geology
The Oklahoma Geological Survey believes the quake occurred along the Wilzetta Fault, which is also known as the Seminole Uplift. The Wilzetta Fault is a 55 miles (88.5 km) long fault zone that runs from central Pottawatomie CountyPottawatomie County, Oklahoma
Pottawatomie County is a county located in the U.S. state of Oklahoma. The population was 65,521 as of the 2000 census. Its county seat is Shawnee...
to the western part of Creek County. It is a strike-slip fault, where two adjacent crustal blocks slide horizontally past each other, but unlike the similar moving San Andreas Fault
San Andreas Fault
The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...
, the Wilzetta Fault is not located near the margins of any tectonic plates. Earthquake activity in this region has been on the rise since 2008, though there is no indication that a more severe earthquake is imminent. From 1972 to 2008, between 2 to 6 earthquakes were recorded annually by the USGS, however 50 were recorded in 2009. The USGS and the Oklahoma Geological Survey are installing more seismometer
Seismometer
Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources...
s to better monitor the increased activity. Aftershocks from the 5.6 quake, including some that can be felt, are expected to last for months. The Oklahoma Geological Survey reported that a minor earthquake swarm which occurred in January 2011 could possibly have been due to hydraulic fracturing
Hydraulic fracturing
Considerable controversy surrounds the current implementation of hydraulic fracturing technology in the United States. Hydraulic fracturing, or fracking, is the process of utilizing pressurized water, or some other liquid, to fracture rock layers and release petroleum, natural gas, or other...
, which is a process used to extract oil from oil wells. However, geologists with the USGS and other entities have made it clear that the 5.6 magnitude quake was entirely due to natural causes.
Damage
Early reports indicated that U.S. Route 62U.S. Route 62 in Oklahoma
In Oklahoma, U.S. Highway 62 runs diagonally across the state, from the Texas state line in far southwestern Oklahoma to the Arkansas state line near Fayetteville. US-62 spends a total of in the Sooner State. The highway passes through fifteen of Oklahoma's counties...
had "buckled
Buckling
In science, buckling is a mathematical instability, leading to a failure mode.Theoretically, buckling is caused by a bifurcation in the solution to the equations of static equilibrium...
" in three locations and that several nearby homes had major damage and there were also numerous reports of broken windows and other minor damage, mostly to residences. Some local residents reported minor masonry damage and a chimney collapsed at one residence, while a few residents near 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...
reported a noise which sounded like thunder in the distance as the earthquake struck. The Oklahoma Department of Emergency Management reported that 2 people suffered minor injuries, 14 homes had various levels of damage, and that Benedictine Hall
Benedictine Hall (Shawnee, Oklahoma)
Benedictine Hall at St. Gregory's University, also known as St. Gregory's Abbey and College, is the central feature of the university, housing its administration, library and most of its classes. Designed by St. Louis architect Victor Klutho, the facility opened in the fall of 1915 in Shawnee,...
at St. Gregory's University
St. Gregory's University
St. Gregory's University is a private, co-educational Catholic liberal arts university. It is one of the oldest institutions of higher learning in the U.S. state of Oklahoma. It has its main campus in Shawnee, and an additional campus in Tulsa.-History:St...
in Shawnee
Shawnee, Oklahoma
Shawnee is a city in Pottawatomie County, Oklahoma, United States. The population was 29,857 at the 2010 census. The city is part of the Oklahoma City-Shawnee Combined Statistical Area; it is also the county seat of Pottawatomie County and the principal city of the Shawnee Micropolitan Statistical...
had one turret collapse and two others damaged, forcing the closure of the building.
Radar imagery
The National Weather ServiceNational Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
(NWS) reported that weather radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...
detected insects, bats and birds which had apparently taken flight immediately after the quake. The NWS radar indicated that the tremors were significant enough that those animals that could leave the ground, did so.