Liquefaction Evidence for One or More Strong Holocene Earthquakes in the WabashValley of Southern Indiana and Illinois, with a Preliminary Estimate of Magnitude

摘要

The authors have discovered hundreds of planar, nearly vertical sand- and gracel-filled dikes that they interpret to have been caused by earthquake-induced liquefaction in the Wabash Valley of southern Indiana and Illinois. Preliminary studies indicate that it is highly possible that many, if not all, of the dikes were formed by a single large earthquake that took place in the Vincennes area sometime between 1,500 and 7,500 years ago. The severity of ground shaking required to have formed the observed dikes for exceeds the strongest level of shaking of any earthquake in the Central United States since the 1811-12 New Madrid earthquakes.