No earthquakes of intensity V or above (Modified Mercalli Scale) have occurred within North Dakota during historical times. Earthquakes centered in Iowa, Minnesota, Montana, and Nebraska, and a few Canadian shocks have been felt in the State. The first instrumentally located earthquake in the history of North Dakota occurred on July 8, 1968. Its intensity did not exceed IV, however.
Two of the earthquakes mentioned in the historical literature occurred before North Dakota achieved statehood in 1889. Thus, details on the precise limits of the felt region are lacking. On October 9, 1872, an earthquake located near Sioux City, Iowa, was felt in western Iowa and the adjoining Dakota Territory. Another earthquake on November 15, 1877, was felt through parts of Nebraska, Iowa, Kansas, Missouri, and the Dakotas. Damage was reported from Sioux City, Iowa, and Columbus and North Platte, Nebraska.
A strong shock on May 15, 1909, was felt over approximately 1,300,000 square kilometers, including parts of North Dakota, South Dakota, and Montana.
Beds swayed and dishes rattled (intensity IV) at Williston from a light shock on October 26, 1946. The tremor, of about 5 seconds duration, was felt by many in the vicinity of Williston; it was also felt at Plentywood, Montana. The magnitude 7.1 earthquake of August 17, near Hebgen Lake, Montana, was felt over an area of approximately 1,500,000 square kilometers, including the extreme western portion of North Dakota. Intensity IV effects were noted at Alexander, Alkabo, Beach, Belfield, Bowman, Cartwright, Crosby, Dore, Grenora, Hanks, Medora, Trotters, and Williston.
The July 8, 1968, earthquake previously mentioned was centered near Huff, where a television set shifted and sounds like thunder were heard (intensity IV). The magnitude 4.4 shock was felt over approximately 7,700 square kilometers of south-central North Dakota. Intensity IV effects were also noted at Bismarck, Fort Rice, Linton, Mandan, Menoken, and Moffit; intensity I to III at Almont, Flasher, Halliday, and Saint Anthony.
Southeastern North Dakota experienced tremors on July 9, 1975, from a magnitude 4.8 earthquake located near Morris, Minnesota. Felt reports were received from Fargo and West Fargo, Casselton, Hankison, and Wahpeton.
Abridged from Earthquake Information Bulletin, Volume 7, Number 6, November - December 1975, by Carl A. von Hake.
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