martyllian
New Member
If we get an earthquake here in the center of the country, its worse than the West coast earthquakes because our ground isnt as solid (If I said that right)
Ive seen the effects of the 200 year old earthquakes, its pretty neat to walk in the middle of what used to be the Misissippi River bed
At the time, I was amazed that history and geography in school and college -Never- say anything about this.Look up the new Madrid, Missouri earthquake if you want an eye opener. There is a good chance that the next big earthquake disaster could be in the mid west
Aw heck, why make you do the work:http://upload.wikimedia.org/wikipedia/en/c/cb/Charleston1895.gif
1811/1812 earthquake series
View to the southwest along the former riverbed of the Mississippi River, just south of the Tennessee/Arkansas state line near Reverie, Tennessee and Wilson, Arkansas (2007)December 16, 1811, 0815 UTC (2:15 a.m.); 8.1 magnitude; epicenter in northeast Arkansas; Mercalli XI. It caused only slight damage to man-made structures, mainly because of the sparse population in the epicentral area. However, landslides and geological changes occurred along the Mississippi River, and large localized waves were caused by fissures opening and closing below the Earth's surface.
December 16, 1811, 1415 UTC (8:15 a.m.); 7.0 magnitude; epicenter in northeast Arkansas; Mercalli X-XI. This shock followed the first earthquake by six hours.
January 23, 1812, 1500 UTC (9 a.m.); 7.8 magnitude; epicenter in the Missouri Bootheel. The meizoseismal area was characterized by general ground warping, ejections, fissuring, severe landslides, and caving of stream banks.
February 7, 1812 (the New Madrid Earthquake), 0945 UTC (4:45 a.m.); ~8 magnitude; epicenter near New Madrid, Missouri. New Madrid was destroyed. At St. Louis, Missouri, many houses were severely damaged, and their chimneys were toppled. The seismic area was characterized by general ground warping, ejections, fissuring, severe landslides, and caving of stream banks.
Geologic effects
Large areas sank into the earth, fissures opened, lakes permanently drained, new lakes were formed, and forests were destroyed over an area of 150,000 acres (610 km2). Many houses at New Madrid were thrown down. "Houses, gardens, and fields were swallowed up" one source notes. But fatalities and damage were low, because the area was sparsely settled.
The earthquakes were felt as far away as New York City and Boston, Massachusetts, where churchbells rang.
Mississippi River course changes
View to the northeast along the former riverbed of the Mississippi RiverThis series of temblors caused permanent changes in the course of the Mississippi River, giving the illusion that it was flowing backward.
Because of the change in the course of the Mississippi River, land was cut off from counties by the river and wound up on the other side of the new riverbed, on the other side of the Mississippi. The settlement of Reverie, Tennessee, in Tipton County was cut off and placed on the western bank of the Mississippi River on the Arkansas side.
Along the Tennessee/Arkansas state line, geological features are still present almost 200 years after the events, showing the former course of the Mississippi River as it was before the 1811/1812 earthquakes.
Focal depth of the earthquakes
Contemporary woodcut of the effects of the New Madrid earthquakesFrom what is known about the present seismicity of the area, it can be inferred that their focal depths were probably between 3 to 12 mi (5-20 km). The fault plane—or planes—on which the Earth rupture occurred are inferred to have had a north-northeast to south-southwest strike direction, more or less parallel to the Mississippi River.
Aftershocks
Hundreds of aftershocks followed over a period of several years. Aftershocks strong enough to be felt occurred until the year 1817. The largest earthquakes to have occurred since then were on January 4, 1843, and October 31, 1895, with magnitude estimates of 6.0 and 6.2 respectively. In addition to these events, nine events of magnitude 5.0 or greater have occurred in the area.
Commemorating the earthquakes
From the early years of the 19th century until well after the American Civil War, the citizens of Union City, Tennessee, would gather every February 7 for an all-night "vigil and fish fry" on the site currently occupied by the Cumberland Presbyterian Church, praying, singing, and beseeching the Almighty to "spare the land over" for another year.
New Fault Discovered Near the New Madrid Seismic Zone (NMSZ)
On January 21, 2009, the director of the Arkansas Earthquake Center at the University of Arkansas announced the discovery of a new fault near Marianna, Arkansas, 100 miles (160 km) east of Little Rock, which could generate a 7.0 earthquake in the future. This fault is close to, but appears to be separate from, the NMSZ.
Future Quakes
Comparison: the 1895 Charleston, Missouri, earthquake in the New Madrid seismic zone with the 1994 Northridge, California, earthquake. Red indicates area of structural damage, yellow indicates area where shaking was felt.In a report filed in November 2008, The U.S. Federal Emergency Management Agency warned that a serious earthquake in the New Madrid Seismic Zone could result in "the highest economic losses due to a natural disaster in the United States," further predicting "widespread and catastrophic" damage across Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri and particularly Tennessee, where a 7.7 magnitude quake or greater would cause damage to tens of thousands of structures affecting water distribution, transportation systems, and other vital infrastructure.[7]
The potential for the recurrence of large earthquakes and their impact today on densely populated cities in and around the seismic zone has generated much research devoted to understanding earthquakes. Establishing the probability for an earthquake of a given magnitude is an inexact science. By studying evidence of past quakes and closely monitoring ground motion and current earthquake activity, scientists attempt to understand their causes, recurrence rates, ground motion and disaster mitigation.
Probability
The probability of magnitude 6.0 or greater in the near future is considered significant; a 90% chance of such an earthquake by 2040 has been given. In the June 23, 2005, issue of the journal Nature, the odds of another 8.0 event within 50 years were estimated to be between 7 and 10 percent.[8]
Because of the unconsolidated sediments which are a major part of the underlying geology of the Mississippi embayment, as well as the river sediments along the Mississippi and Ohio River valleys to the north and east (note the red fingers extending up these valleys in the image above), large quakes have the potential for more widespread damage than major quakes on the west coast. Additionally, the area affected will be larger since beyond the rift zone itself there are few other faults to attenuate the seismic waves.
