The 1983 Borah Peak earthquake occurred on October 28, at in the

western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, in the

Lost River Range The Lost River Range is a high mountain range of the Rocky Mountains, located in Central Idaho, in the Northwestern United States. It runs southeast for approximately from the Salmon River near the community of Challis to the Snake River Val ...

Borah Peak Borah Peak, also known as Mount Borah or Beauty Peak, is the highest mountain in the U.S. state of Idaho and one of the most prominent peaks in the contiguous United States. It is located in the central section of the Lost River Range, within th ...

central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

. The shock measured 6.9 on the

moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mw, 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. It was defined in a 1979 pape ...

and had a maximum

Mercalli intensity The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

of IX (''Violent''). It was the most violent earthquake in the

lower 48 states The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...

in over 24 years, since the 1959 Hebgen Lake earthquake in nearby

southwestern The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sepa ...

Earthquake

The Friday morning earthquake was caused by a slip on the preexisting Lost River Fault. The event is the largest and most significant to strike in the state of Idaho. Two children were killed by falling masonry while walking to school in about northeast of

Boise Boise (, , ) is the capital and most populous city of the U.S. state of Idaho and is the county seat of Ada County. On the Boise River in southwestern Idaho, it is east of the Oregon border and north of the Nevada border. The downtown area' ...

, the state capital. Twelve-and-a-half million

dollars Dollar is the name of more than 20 currencies. They include the Australian dollar, Brunei dollar, Canadian dollar, Hong Kong dollar, Jamaican dollar, Liberian dollar, Namibian dollar, New Taiwan dollar, New Zealand dollar, Singapore dollar, U ...

in damage took place in the Challis-

Mackay Mackay may refer to: *Clan Mackay, the Scottish clan from which the surname "MacKay" derives Mackay may also refer to: Places Australia * Mackay Region, a local government area ** Mackay, Queensland, a city in the above region *** Mackay Airpor ...

region in Custer County. As a result of extreme surface faulting, a maximum

of IX (''Violent'') was decided upon, while vibrational damage was at a Mercalli intensity of VI (''Strong'') to VII (''Very strong''). Three weeks later on November 18,

President President most commonly refers to: *President (corporate title) *President (education), a leader of a college or university *President (government title) President may also refer to: Automobiles * Nissan President, a 1966–2010 Japanese ful ...

Ronald Reagan Ronald Wilson Reagan ( ; February 6, 1911June 5, 2004) was an American politician, actor, and union leader who served as the 40th president of the United States from 1981 to 1989. He also served as the 33rd governor of California from 1967 ...

declared the earthquake a

Aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousand ...

s were felt for a year afterwards; nearly ten months later, a 5.4 aftershock was recorded on

Surface faulting

The rupture caused clear surface faulting; a long northwest-trending zone of fresh scarps and ground ruptures was present on a slope of the

. Extensive breakage occurred along a zone between West Spring and Cedar Creek; ground surface was literally "shattered" into tilted blocks, each several meters in width. These scarps were as broad as . The ground breakage was , and the throw on the faulting ranged from .

Damage

The Challis-Mackay region experienced rather thorough damage, with eleven commercial buildings and 39 homes sustaining major damage while another 200 houses suffered minor to moderate damage.

in particular, about southeast of Challis, experienced the most severe damage. Most of the city's large buildings on its Main Street were damaged, to some extent; eight of these buildings were deemed condemned and closed down. Most of these buildings were built from materials such as brick, concrete block, and stone, each varying. An estimated $12.5 million in property damage was recorded. In some places, the water grounds shifted.

Fatalities and injuries

In Challis, two children were killed when a stone storefront collapsed on them while walking to school; two others suffered minor injuries. In Mackay, a woman was hospitalized due to her injuries.

Old Faithful

After the earthquake and aftershocks, the eruption intervals of

Old Faithful Old Faithful is a cone geyser in Yellowstone National Park in Wyoming, United States. It was named in 1870 during the Washburn–Langford–Doane Expedition and was the first geyser in the park to be named. It is a highly predictable geotherm ...

geyser in

Yellowstone National Park Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowston ...

, about east, were noticeably lengthened.

Sand blows

Near Chilly Buttes of Thousand Springs Valley, a series of artesian fountains/sand blows erupted immediately after the main shock. Groundwater gushed from these fountains forming small craters and depositing aprons of light-colored sandy sediment around each crater. The blows were noted largely along waterways, especially where draws, or small streams, enter into larger ones. Observers noted that some blows have black, sediment laden water while others ran mostly clear. Some blows continued for several minutes after the shaking stopped. The Big Lost River rose several inches as a result of this water being expelled from the ground. The eruptions were likely a response to liquefaction of a water laden underground sediment layer. File:Fault Scarp Borah Peak Earthquake 1983.jpg, Fault scarps that outline the

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic contex ...

produced near Willow Creek File:Borah Peak earthquake artesian fountain 1983.jpg, Crater caused by an artesian fountain File:Borah Peak earthquake artesian fountain 1983b.jpg, Another view of the same fountain

References

External links

Borah Peak earthquake
– Idaho Geological Survey
M 6.9 - southern Idaho
–

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the 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, ...

Two children die as quake hits northwest and Canada
– ''

The New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...

'' * {{Authority control Borah Peak Earthquake, 1983 Earthquakes in Idaho 1983 in Idaho