1968 Illinois earthquake

1968 Illinois earthquake
Intensity VI and VII levels are mostly in southeast Illinois, with some small nearby regions in Indiana, Kentucky, Tennessee, and Missouri. Intensity V or greater covers the southern half of Illinois, the western quarter of Kentucky, and smaller parts of adjacent states. Intensity IV or greater covers most of Illinois, Indiana, Missouri, Tennessee, and Kentucky, as well as portions of neighboring states. Intensity I or greater is present in 22 U.S. states and the southernmost tip of Canada.
Isoseismal map for the event (I–III are Not felt to Weak, IV is Light, V is Moderate, VI is Strong, VII is Very strong)
UTC time1968-11-09 17:01:38
ISC event814965
USGS-ANSSComCat
Local dateNovember 9, 1968 (1968-11-09)
Local time11:01:40 CST
Magnitude5.3 mb[1]
Depth19 km (12 mi)[2]
Epicenter37°57′N 88°29′W / 37.95°N 88.48°W / 37.95; -88.48[3]
TypeDip-slip
Max. intensityMMI VII (Very strong)
CasualtiesNone

The 1968 Illinois earthquake (a New Madrid event)[4] was the largest recorded earthquake in the U.S. Midwestern state of Illinois. Striking at 11:02 a.m. on November 9, it measured 5.3 on the Richter scale.[5] Although no fatalities occurred, the event caused considerable structural damage to buildings, including the toppling of chimneys and shaking in Chicago, the region's largest city. The earthquake was one of the most widely felt in U.S. history, largely affecting 23 states over an area of 580,000 sq mi (1,500,000 km2). 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; in 2005, seismologists and geologists estimated 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.

  1. ^ International Seismological Centre. Event Bibliography. Thatcham, United Kingdom. [Event 814965].
  2. ^ ISC-EB Event 814965 [IRIS]
  3. ^ Cite error: The named reference BSSA was invoked but never defined (see the help page).
  4. ^ Hough 2002, p. 209.
  5. ^ "Illinois Earthquake Information". United States Geological Survey. July 16, 2008. Archived from the original on 16 December 2008. Retrieved November 9, 2008.

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