Geology topics
Publications and source records attributed to C. A. von Hake.
Seventeen earthquakes, intensity V or greater, have centered in Texas since 1882, when the first shock was reported. The strongest earthquake, a maximum intensity VIII, was in western Texas in 1931 and was felt over 1 165 000 km 2 . Three shocks in the Panhandle region in 1925, 1936, and 1943 were widely felt.
The western part of the State was shaken strongly by the New Madrid, Mo., earthquakes of 1811-12 and by earthquakes in 1843 and 1895. The area has also experienced minor shocks. Additional activity has occurred in the eastern part of the State, near the North Carolina border. Forty shocks of intensity V (Modified Mercalli scale) or greater have been cataloged as occurring within the State. Many other earthquakes centered in bordering States have affected points in Tennessee. The following summary covers only hose shocks of intensity VI or greater.
Twelve earthquakes of intensity V or greater (Modified Mercalli scale) have centered within the borders of South Dakota. All the shocks were rather localized, except that of 1911 which was felt over an area of approximately 100,000 km 2 . Some earthquakes from neighboring States were felt strongly in South Dakota.
An estimated $23 million damage was caused by one of the great earthquakes in United States history in 1886. Charleston, S.C, and nearby cities suffered most of the damage, although points as far as 160 km away were strongly shaken. Many of the 20 earthquakes of intensity V or greater (Modified Mercalli scale) that centered within South Carolina occurred near Charleston. A 1924 shock in the western part of the State was felt over 145,000 km 2 . Several earthquakes outside the State borders were felt strongly in South Carolina.
Only three shocks (intensity V or greater, Modified Moercalli Scale) have centered in Rhode Island, although several earthquakes in New England and the St.Lawerence Valley have been felt in the State.
Record of early earthquakes in Northeastern United States provide limited information on effects in pennsylvania until 1737, 55 years after the first permanent settlement was established. A very severe earthquake that centered in the St.Lawrence River region in 1663 may have been felt in Pennsylvania, but historical accounts are not definite. Likewise, a damaging shock at Newbury, Mass., in 1727 probably affected towns in Pennsylvania. A strong earthquake on December 18, 1737, toppled chimneys at New York City and was reported felt at Boston, Mass., Philadelphia, Pa. and New Castle, Del. Other shocks with origins outside the State were felt in 1758, 1783, and 1791. Since 1800, when two earthquakes (March 17 and November 29) were reported as "severe" at Philadelphia, 16 tremors of intensity V or greater (Modified Mercalli Scale) have originated within the State. On November 11 and 14, 1840, sever earthquakes at Philadelphia were accompnaied by a great and unusual swell on the Delaware River.
Although situated between two States (California and Washington) that have has many violent earthquakes, Oregon is noticeably less active seismically. the greatest damage experienced resulted from a major shock near Olympia, Wash., in 1949. During the short history record available (since 1841), 34 earthquakes of intensity V, Modified Mercalli Scale, or greater have centered within Oregon or near its borders. Only 13 of the earthquakes had an intensity above V, and many of the shocks were local. However, a 1936 earthquake in the eastern Oregon-Washington region caused extensive damage and was felt over an area of 272,000 square kilometers.
The strongest and most widely felt earthquake in Oklahoma occurred on April 9, 1952. The intensity VII (Modified Mercalli Scale) tremor was felt over 362,000 sqaure kilometres. A second intensity VII earthquake, felt over a very small area, occurred in October 1956. In addition, 15 other shocks, intensity V or VI, have originated within Oklahoma.
Most of New Mexico's historical seismcity has been concentrated in the Rio Grande Valley between Socorro and Albuquerque. About half of the earthquakes of intensity V or greater (Modified Mercalli intensity) that occurred in teh State between 1868 and 1973 were centered in this region.
Since 1852, more than 30 shocks of intensity VI or greater (Modified Mercalli scale) have occurred in western Nevada. At least three of these were classified as intensity X. In addition, seven earthquakes (intensity VI or greater) were centered in the eastern part of the State. Almost 2,000 other shocks have been cataloged in the nearly 125-year period of historical records. Thus, Nevada ranks among the most seismically active States.
Nebraska is in a region of moderate seismicity occasionally punctuated by rather strong earthquakes. Most of the State is seismic risk zone 1, with a small part in the southeast corner in risk zone 2. the first significant earthquake felt in Nebraska occurred in 1867, the year that statehood was achieved. the tremor occurred on April 24, 1867, and was apparently centered near Lawrence, Kansas. It affected an area estimated at 780,000 km 2 including much of Nebraska. Since 1867, at least seven earthquakes of intensity V or greater have originated within Nebraska's boundaries. Several strong earthquakes centered in neighboring States have also been felt over limited portions of Nebraska. None of these caused damage.
Montana is one of the most seismically active States in the Union. Since 1925, the State has experienced five shocks that reached intensity VIII or greater (Modified Mercalli Scale). During the same interval hundreds of less severe tremors were felt within the State. Montana's earthquake activity is concentrated mostly in the mountainous western third of the State which lies within a seismic zone that also includes southeastern Idaho, western Wyoming, and central Utah.
Most of Missouri's earthquake activity has been concentrated in the southeast corner of the State, which lies within the New Madrid seismic zone. As recently as Merch 29, 1972, the region was jolted by a magnitude 3.7 shock that was felt over a 168,000 square kilometre area including parts of Arkansas, Illinois, Mississippi, and Tennessee.
Since its admission into the Union in 1817, Mississippi has had only four earthquakes of intensity V or greater within its borders. Although the number of earthquakes known to have been centered within Mississippi's boundaries is small, the State has been affected by numerous shocks located in neighboring States. In 1811 and 1812, a series of great earthquakes near the New Madrid Missouri area was felt in Mississippi as far south as the gulf coast. The New Madrid series caused the banks of the Mississippi River to cave in as far as Vicksburg, mroe than 300 miles from the epicentral region. As a result of this great earthquake series, the northwest corner of Mississippi is in seismic risk zone 3, the highest risk zone. Expect for the new Madrid series, effects in Mississippi from earthquakes located outside of the State have been less than intensity V.
French traders and missionaries were active in the region that is now Minnesota as early as the 1650's; however, settlement proceeded slowly and the area was not organized as a territory until 1849. Minnesota was admitted to the Union as the 32nd State on May 11, 1858. the earthquake history of the State is incomplete, owing to the scarity of residents prior to the middle of the 19th century.
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