Last Friday's magnitude 5.2 earthquake in southern Illinois is a reminder that earthquakes are a national hazard.
Today, scientists at the U.S. Geological Survey (USGS) are revealing how shaky the nation is by releasing an updated version of the USGS National Seismic Hazard Maps.
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©U.S. Geological Survey
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Colors on this map show the levels of horizontal shaking that have a 2-in-100 chance of being exceeded in a 50-year period. Shaking is expressed as a percentage of g (g is the acceleration of a falling object due to gravity).
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Earthquakes remain a serious threat in 46 of the United States. For some areas such as western Oregon and Washington, the new maps contain higher estimates for how hard the ground will shake compared to earlier versions of the maps released in 1996 and 2002.
Comment: Chapman has it only partly right. He excludes the evidence for cometary dust loading that contributed to the last ice age (and most likely previous ones). The increased depositional flux evidenced from Gabrielli's paper shows that it was not the sun alone that caused the last ice age:
And from Victor Clube's talk: Now the question must be asked, Is there a relationship between the sun's missing spots and a 100,000 year ice age cycle coupled with cometary debris entering the solar system?