The 1975 Morris earthquake occurred in western

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

on July 9 at 14:54:15 UTC, or 9:54 a.m. The strongest instrumentally recorded rupture in the history of the state, it registered at magnitude 4.6 M_n 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 VI (''Strong''). It was the first

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

to be recorded on any seismic instrument in the state since 1917. Tremors were felt over much of Minnesota, northern Iowa, and the eastern Dakotas.

Setting

Minnesota is not a very tectonically active state; however, there is at least one fault zone in it, the Great Lakes Tectonic Zone, stretching from Big Stone County and Traverse County to

Duluth , settlement_type = City , nicknames = Twin Ports (with Superior), Zenith City , motto = , image_skyline = , image_caption = Clockwise from top: urban Duluth skyline; Minnesota ...

. Seventeen earthquakes have occurred along the fault, the two largest being the Morris quake and the Staples event of 1917. However, plotting of the earthquakes suggests that there may be another hidden fault in the state somewhat adjacent to it.

Damage

The earthquake caused moderate damage and was defined as intensity VI on the

Mercalli intensity scale 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 ...

. Minor damage to walls and basement foundations was reported around the

epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

in Stevens County. Damage consisted of cracked plaster, falling items, and pictures being knocked off walls. The quake also cracked the foundations of two homes on East Fifth Street in

Morris Morris may refer to: Places Australia *St Morris, South Australia, place in South Australia Canada * Morris Township, Ontario, now part of the municipality of Morris-Turnberry * Rural Municipality of Morris, Manitoba ** Morris, Manitob ...

. Many reports included extremely loud "bangs" and "explosions". These sounds lead to one man thinking that a nearby gas plant had exploded. If the earthquake had occurred elsewhere, however, it may have caused a larger amount of damage.

References

External links

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Today in Earthquake History
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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, ...

{{DEFAULTSORT:Morris Earthquake, 1975 1975 earthquakes

1975 It was also declared the ''International Women's Year'' by the United Nations and the European Architectural Heritage Year by the Council of Europe. Events January * January 1 - Watergate scandal (United States): John N. Mitchell, H. R. ...

Setting

Damage

See also

References

External links