EARTHQUAKES IN ILLINOIS Although we tend to think of California and Alaska as the places where most of our earthquakes occur, the fact is that the central U.S. has been the site of some very powerful earthquakes.

THE TEN LARGEST EARTHQUAKES IN THE UNITED STATES Mag.Date (UTC)Location March 28, 1964Prince William Sound, Alaska March 9, 1957Andreanof Islands, Alaska February 4, 1965Rat Islands, Alaska November 10, 1938E of Shumagin Islands, Alaska 8.3 July 10, 1958Lituya Bay, Alaska September 10, 1899Yakutat Bay, Alaska 8.2September 4, 1899Near Cape Yakataga, Alaska May 7, 1986Andreanof Islands, Alaska February 7, 1812New Madrid, Missouri 7.9January 9, 1857Fort Tejon, California 7.9April 3, 1868Ka'u District, Island of Hawaii 7.9October 9, 1900Kodiak Island, Alaska 7.9 November 30, 1987Gulf of Alaska

THE TEN LARGEST EARTHQUAKES IN THE CONTIGUOUS U.S. Mag.Date (UTC)Location February 7, 1812New Madrid, Missouri 7.9January 9, 1857Fort Tejon, California March 26, 1872Owens Valley, California 7.8February 24, 1892Imperial Valley, California December 16, 1811New Madrid, Missouri area 7.7April 18, 1906San Francisco, California 7.7October 3, 1915Pleasant Valley, Nevada January 23, 1812New Madrid, Missouri July 21, 1952Kern County, California November 4, 1927West of Lompoc, California 7.3December 16, 1954Dixie Valley, Nevada 7.3August 18, 1959Hebgen Lake, Montana 7.3October 28, 1983Borah Peak, Idaho

1997 EARTHQUAKES

The three earthquakes that occurred in 1811 and 1812 near New Madrid, MO. are among the Great earthquakes of known history, affecting the topography more than any other earthquake on the North American continent. Judging from their effects, they were of a magnitude of 8.0 or higher on the Richter Scale. They were felt over the entire United States outside of the Pacific coast. Large areas sank into the earth, new lakes were formed, the course of the Mississippi River was changed.

The 1st and 2nd earthquakes occurred in Arkansas on December 16, These earthquakes caused only slight damage to man-made structures, mainly because of the sparse population in the epicentral area. The extent of the area that experienced damaging earth motion (MM intensity greater than or equal to VII) is estimated to be 600,000 square kilometers. However, shaking strong enough to alarm the general population (MM intensity greater than or equal to V) occurred over an area of 2.5 million square kilometers.

1812, January 23, 15:00 UTC, New Madrid, Missouri Using the December 16 earthquake as a standard, a comparison between it and the shock on January 23 indicates that the intensities were about equal at similar locations.

1812, February 7, 09:45 UTC, New Madrid, Missouri This is the fourth and largest earthquake of the series. Several destructive shocks occurred on February 7, the last of which equaled or surpassed the magnitude of any previous event. The town of New Madrid was destroyed. At St. Louis, many houses were damaged severely and their chimneys were thrown down. The area was characterized by general ground warping, ejections, fissuring, severe landslides, and caving of stream banks.

The Mercalli Scale measures damage caused by an earthquake Uses Roman Numerals I – XII I is the weakest XII is the strongest

The probability for an earthquake of magnitude 6.0 or greater is significant in the near future, with a 50% chance by the year 2020 and a 90% chance by the year A quake with a magnitude equal to that of the quakes could result in great loss of life and property damage in the billions of dollars. Scientists believe we could be overdue for a large earthquake.

NEW MADRID EARTHQUAKES NOV 1-14,2001