The Denali Fault is a major intracontinental dextral (right lateral)

strike-slip fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

in western

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, extending from northwestern

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

to the central region of the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its so ...

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

Location

The Denali Fault is located in the southern half of Alaska in the

Alaska Range The Alaska Range is a relatively narrow, mountain range in the Southcentral Alaska, southcentral region of the U.S. state of Alaska, from Lake Clark at its southwest endSources differ as to the exact delineation of the Alaska Range. ThBoard on G ...

. It is more than 1,250 miles long, arcing through southern Alaska, southwestern

Yukon Yukon () is a Provinces and territories of Canada, territory of Canada, bordering British Columbia to the south, the Northwest Territories to the east, the Beaufort Sea to the north, and the U.S. state of Alaska to the west. It is Canada’s we ...

, and back into southeastern Alaska. The steep north face of

Denali Denali (), federally designated as Mount McKinley, is the highest mountain peak in North America, with a summit elevation of above sea level. It is the tallest mountain in the world from base to peak on land, measuring . On p. 20 of Helm ...

, known as the Wickersham Wall, rises 15,000 feet from its base, and is a result of relatively recent vertical movement along the fault.

Effects

Alaska's network of faults is a result of tectonic activity; the Pacific plate is actively subducting (sliding under) the North American plate, and the Denali Fault is located on the boundary between the two plates. Along the Denali Fault, lateral and vertical offset movement is taking place at a rate of approximately 13 mm/yr. Around 300 to 400 kilometers of displacement has occurred since the Cretaceous, and about 25% of that displacement has occurred since the Miocene. According to tree ring studies, a magnitude 7.2 to 7.4 earthquake happened along the fault in 1912. It was the main fault along which the

2002 Denali earthquake The 2002 Denali earthquake occurred at 22:12:41 UTC (1:12 PM Alaska Time Zone, Local Time) November 3 with an epicenter 66 km ESE of Denali National Park, Alaska, United States. This 7.9 Moment magnitude scale, Mw earthquake was the larges ...

occurred, which was measured as 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 ...

of 7.9 ''M_w''. During the afternoon of November 3, 2002, the water in Seattle's Lake Union suddenly began sloshing hard enough to knock houseboats off their moorings. Water in pools, ponds, and bayous as far away as

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

and

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splashed for nearly half an hour. The earthquake began at 1:12 p.m.

local time, and was centered approximately 135 kilometers (84 miles) south of Fairbanks and 283 kilometers (176 miles) north of

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 ...

. Shaking at the epicenter lasted approximately 1.5 to 2 minutes, but in Fairbanks the duration of the earthquake was over 3 minutes. Originating on the previously unknown Susitna Glacier Fault, the earthquake shot eastward along the well-known Denali Fault at a speed of over 11,265 kilometers (7,000 miles) per hour before branching southeast onto the

Totschunda Fault The Totschunda Fault is a major active dextral (right-lateral) continental strike-slip fault in southeastern Alaska. It forms a link between the Denali Fault to the northwest and the Fairweather Fault to the southeast. The northwestern end of the ...

. The resulting

surface rupture In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a Fault (geology), fault affects the Earth's surface. Surface rupture is opposed by buried rup ...

was approximately 336 kilometers (209 miles) long, and it cut through streams, divided forests, opened chasms in roads, and even generated

fault trace A fault trace describes the intersection of a Fault (geology), geological fault with the Earth's surface, which leaves a visible disturbance on the surface, usually looking like a crack in the surface with jagged rock structures protruding outwar ...

s visible across several glaciers. Because the earthquake released most of its energy on the sparsely populated eastern end of the fault, Alaska's major cities were spared serious damage.

References

{{Faults Seismic faults of Canada Seismic faults of Alaska Geology of British Columbia Geology of Yukon Strike-slip faults Supershear earthquakes

Location

Effects

See also

References