1983 Borah Peak earthquake

1983 Borah Peak earthquake
Borah Peak with fault scarp seen near base of tan hill in foreground
Challis Boise
Date	October 28, 1983
Origin time	14:06:09 UTC ^[1]
Magnitude	6.9 M_w ^[1]
Depth	16 km (9.9 mi) ^[2]
Epicenter	44°05′N 113°48′W / 44.08°N 113.8°W / 44.08; -113.8Coordinates: 44°05′N 113°48′W / 44.08°N 113.8°W / 44.08; -113.8 ^[2]
Type	Dip-slip ^[3]
Areas affected	Central Idaho United States
Total damage	$12.5 million USD ^[4]
Max. intensity	IX (Violent) ^[4]
Landslides	Yes
Aftershocks	5.6 M_w Oct 28 at 19:51 UTC ^[2] 5.5 M_w Oct 29 at 23:29 UTC ^[2]
Casualties	2 killed, three injured ^[2]

The 1983 Borah Peak earthquake occurred on October 28 at 8:06:09 local time in the Lost River Range at Borah Peak in central Idaho, United States. The shock measured 6.9 on the moment magnitude scale and had a maximum Mercalli intensity of IX (Violent).

Earthquake

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 Challis, about 120 miles (200 km) northeast of Boise, the state's capital. Twelve and a half million dollars in damage took place in the Challis-Mackay region. As a result of extreme surface faulting, a maximum Mercalli intensity of IX (Violent) was decided upon, while vibrational damage was at a Mercalli intensity of VI (Strong) to VII (Very strong).^[4]

Surface faulting

The rupture caused clear surface faulting. A 21-mile (34 km) long northwest-moving zone of fresh scarps and ground ruptures was present on a slope of the Lost River Range. Extensive breakage occurred along a 5-mile (8 km) zone between West Spring and Cedar Creek; ground surface was literally "shattered" into tilted blocks, each meters in width. These scarps were as broad as 330 feet (100 m).^[4]

Damage

The Challis-Mackay region experienced rather thorough damage, with 11 commercial buildings and 39 homes with major damage; while another 200 houses were damaged, minor to moderately. Mackay in particular, about 50 miles (80 km) 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.^[4]

Sand blows

Further information: Sand volcano

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.

Fault scarps that outline the graben produced near Willow Creek
Crater caused by an artesian fountain
Another view of an artesian fountain

References

1 2 ISC (2015), ISC-GEM Global Instrumental Earthquake Catalogue (1900–2009), Version 2.0, International Seismological Centre
1 2 3 4 5 USGS (September 4, 2009), PAGER-CAT Earthquake Catalog, Version 2008_06.1, United States Geological Survey
↑ Yeats, R. (2012), Active Faults of the World, Cambridge University Press, pp. 125, 135, ISBN 978-0-521-19085-5
1 2 3 4 5 Stover, C. W.; Coffman, J. L. (1993), Seismicity of the United States, 1568–1989 (Revised) – U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, pp. 216–221

External links

Borah Peak earthquake – Idaho Geological Survey
Historic Earthquakes (Borah Peak, Idaho ) – United States Geological Survey
Two children die as quake hits northwest and Canada – The New York Times

← Earthquakes in 1983 →

Coalinga (6.5, May 2) Noshiro (7.8, May 26) † Biga (6.1, July 5) Kopaonik (5.3, September 10) Borah Peak (6.9, October 28) Erzurum (6.9, October 30) † ‡ Chagos Archipelago (7.7, November 30)

† indicates earthquake resulting in at least 30 deaths ‡ indicates the deadliest earthquake of the year

Earthquakes in the United States

Historical	1638 New Hampshire 1663 Charlevoix 1700 Cascadia 1755 Cape Ann 1811–12 New Madrid 1812 Wrightwood 1838 San Andreas 1857 Fort Tejon 1865 Memphis 1867 Manhattan, Kansas 1868 Hawaii 1868 Hayward 1872 Lone Pine 1872 North Cascades 1886 Charleston 1887 Sonora 1892 Laguna Salada 1892 Vacaville–Winters

20th-century	1906 San Francisco 1906 Aleutian Islands 1909 Wabash River 1915 Pleasant Valley 1916 Irondale 1918 San Jacinto 1925 Santa Barbara 1931 Valentine 1932 Eureka 1933 Long Beach 1935 Helena 1940 El Centro 1940 New Hampshire 1944 Cornwall–Massena 1946 Aleutian Islands 1947 Wisconsin 1948 Desert Hot Springs 1949 Olympia 1952 Kern County 1957 Andreanof Islands 1957 San Francisco 1959 Hebgen Lake 1964 Alaska 1965 Rat Islands 1965 Puget Sound 1968 Illinois 1969 Santa Rosa 1971 San Fernando 1975 Near Islands 1975 Morris 1975 Hawaii 1979 Coyote Lake 1979 Imperial Valley 1980 Eureka 1983 Coalinga 1983 Borah Peak 1984 Morgan Hill 1986 North Palm Springs 1986 Chalfant Valley 1987 Whittier Narrows 1989 Loma Prieta 1990 Upland 1991 Sierra Madre 1992 Cape Mendocino 1992 Landers 1992 Big Bear 1993 Scotts Mills 1993 Klamath Falls 1994 Northridge 1995 Marathon 1996 Duvall 1998 Pymatuning 1999 Hector Mine 2000 Yountville

21st-century	2001 Nisqually 2002 Denali 2003 Alabama 2003 San Simeon 2006 Gulf of Mexico 2006 Hawaii 2007 Alum Rock 2008 Illinois 2008 Chino Hills 2010 Eureka 2010 Illinois 2010 Baja California 2010 Indiana 2011 Colorado 2011 Virginia 2011 Oklahoma 2014 Aleutian Islands 2014 Southeast Alaska 2014 South Napa 2016 Oklahoma

Swarms	2001 Enola 2008 Reno 2010–11 Guy-Greenbrier 2012 Brawley 2009–16 Oklahoma

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