Steven Dutch University of Wisconsin - Green Bay
|A computer printout from the U.S. Geological Survey lists 19 Wisconsin events and 11 more around Houghton in the Upper Peninsula of Michigan. They are shown in the map at left and the table below. None were large or destructive.
If it looks like the earthquakes are targeting cities, it's because these records (mostly old) are based mostly on felt reports, and the observers tended to be concentrated in cities. Several events plot neatly on the Illinois boundary because the computer listing gave a neatly rounded latitude for a location estimate.
|1964||October 10||Apostle Islands||?||?|
|1905||July 27||Houghton, MI||?||?|
|1906||February 9||Houghton, MI||?||?|
|1906||April 20||Houghton, MI||?||?|
|1906||May 25||Houghton, MI||?||?|
|1906||May 26||Houghton, MI||?||?|
|1906||September 11||Houghton, MI||?||?|
|1909||January 23||Houghton, MI||?||?|
|1915||March 3||Houghton, MI||?||?|
|October 4||Houghton, MI||?||?|
|1918||October 1||Houghton, MI||?||?|
|1922||July 7||Fond du Lac||4.2||V|
|1956||July 18||Lake Church||3.8||IV|
|1947||May 6||West Allis||4.2||V|
|1933||December 6||SE Dane County||3.8||IV|
|1907||November 20||SW Green County||3.8||IV|
|1907||November 28||SW Green County||3.8||IV|
|1948||January 15||Sauk City||4.0||V|
|1938||November 7||Extreme SW Corner||?||?|
Earthquake History of the United States, U.S. Geological Survey Publication 41-1 (1982 edition) lists no Wisconsin earthquakes but lists quite a few out-of-state events as being felt in Wisconsin. Some that plot on the borders of Wisconsin are on the above map but are listed under Michigan or Illinois. In recent years, the most common source of Wisconsin felt reports has been earthquakes in southern Illinois (related to the New Madrid earthquake area) that were felt in tall buildings in Milwaukee.
Seismicity of the United States 1568-1989 (U.S. Geological Survey Professional Paper 1527) also lists no earthquakes for Wisconsin (only Iowa and North Dakota also have no listings). This publication covers only earthquakes of magnitude 4 and above, however. It describes the Houghton event of January, 1909 as due to geological instability due to mining and the cluster of events in that area may all have a similar origin.
The status of the earthquakes on the map is unclear. Considering the fuzziness of the record and the lack of recent events, there is some reason to question how many of these events were real earthquakes. Some may have been real, some may have been quarry collapses or blasts. There is a significant possibility that there have been no earthquakes centered in Wisconsin in recorded history.
|1663||February 5||St. Lawrence Valley||Felt by French missionaries in Wisconsin|
|1886||August 31||Charleston, South Carolina||Famous Great Earthquake|
|1909||May 26||Illinois Border||Plotted on Map|
|1909||September 27||Western Indiana|
|1912||January 2||Northern Illinois|
|1917||April 9||Eastern Missouri|
|1925||February 28||St. Lawrence Valley||Magnitude 7 Event|
|1935||November 1||Northeastern Ontario|
|1937||March 2||Western Ohio|
|1937||March 8||Western Ohio|
|1939||November 23||Southern Illinois|
|1947||August 9||South-Central Michigan|
|1968||November 9||Southern Illinois|
|1972||September 15||Northern Illinois|
|1974||April 3||Southern Illinois|
|1987||June 10||Northern Illinois|
Cryogenic earthquakes are disturbances related to ground freezing. They can occur when expansion of ice in freezing ground causes ice and already frozen soil to rupture, or when thawing releases pent-up stresses in still-frozen ground. They are not related to any deep tectonic forces within the crust. They rarely cause damage except perhaps at the rupture itself, and are usually felt over a radius of a few hundred yards at most. Because they occur sporadically, are not related to crustal faults, and are felt over such small areas, there is little data on them.
Created 12 Sept 1997, Last Update 3 May 1999