Wikipedia:Today's featured article/November 8, 2009



The 1968 Illinois earthquake was the largest recorded earthquake in the state of Illinois, measuring 5.4 on the Richter scale. Although there were no fatalities, the earthquake caused considerable structural damage to buildings, including the toppling of chimneys. The earthquake was one of the most widely felt in U.S. history, affecting 23 states over an area of 580000 sqmi. In studying its cause, scientists discovered the Cottage Grove Fault in the Southern Illinois Basin. Within the region, millions felt the rupture. Reactions to the earthquake varied: some people near the epicenter did not react to the shaking, while others panicked. A future earthquake in the region is extremely likely; seismologists and geologists estimate a 90% chance of a magnitude 6–7 tremor before 2055, likely originating in the Wabash Valley seismic zone on the Illinois–Indiana border, or the New Madrid fault zone. The first record of seismic activity in Illinois is from 1795, when a small earthquake shook the frontier settlement of Kaskaskia. Data from large earthquakes—in May and July 1909, and November 1968—suggest that earthquakes in the area are of moderate magnitude but can be felt over a large geographical area. (more...)

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