It woke me up. I didn't originally post because it didn't seem like a big deal, but, at 10:15, just a few minutes ago, I think we had another one. (Something shook my desk and chair for about 20 seconds or so.) This is the first time I can recall feeling an aftershock.
Posts: 16662 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
On the basis of the large area of damage (600,000 square kilometers), the widespread area of perceptibility (5,000,000 square kilometers), and the complex physiographic changes that occurred, the Mississippi River valley earthquakes of 1811-1812 rank as some of the largest in the United States since its settlement by Europeans. The area of strong shaking associated with these shocks is two to three times larger than that of the 1964 Alaska earthquake and 10 times larger than that of the 1906 San Francisco earthquake.
This would make a total of five earthquakes of magnitude MSn 8.0 or higher occurring in the period December 16, 1811 through February 7, 1812.
The first earthquake caused only slight damage to man-made structures, mainly because of the sparse population in the epicentral area. The extent of the area that experienced damaging earth motion (MM intensity greater than or equal to VII) is estimated to be 600,000 square kilometers. However, shaking strong enough to alarm the general population (MM intensity greater than or equal to V) occurred over an area of 2.5 million square kilometers.
At the onset of the earthquake the ground rose and fell - bending the trees until their branches intertwined and opening deep cracks in the ground. Landslides swept down the steeper bluffs and hillslides; large areas of land were uplifted; and still larger areas sank and were covered with water that emerged through fissures or craterlets. Huge waves on the Mississippi River overwhelmed many boats and washed others high on the shore. High banks caved and collapsed into the river; sand bars and points of islands gave way; whole islands disappeared. Surface rupturing did not occur, however. The region most seriously affected was characterized by raised or sunken lands, fissures, sinks, sand blows, and large landslides that covered an area of 78,000 - 129,000 square kilometers, extending from Cairo, Illinois, to Memphis, Tennessee, and from Crowleys Ridge to Chickasaw Bluffs, Tennessee.
Although the motion during the first shock was violent at New Madrid, Missouri, it was not as heavy and destructive as that caused by two aftershocks about 6 hours later. Only one life was lost in falling buildings at New Madrid, but chimneys were toppled and log cabins were thrown down as far distant as Cincinnati, Ohio; St. Louis, Missouri; and in many places in Kentucky, Missouri, and Tennessee. -------- Below from CNN, during the 4:30 quake this morning. (The epicenter for this one was about 125 due east of where I live.)
The New Madrid Earthquake, one of the largest earthquakes ever recorded in the contiguous United States, occurred on February 7, 1812. It got its name from its primary location in the New Madrid Seismic Zone, near New Madrid, Louisiana Territory (now Missouri).
This earthquake was preceded by three other major quakes: two on December 16, 1811, and one on January 23, 1812. These earthquakes destroyed approximately half the town of New Madrid. There were also numerous aftershocks in the area for the rest of that winter.
There are estimates that the earthquakes were felt strongly over 50,000 square miles (130,000 km²), and moderately across nearly one million square miles. The historic San Francisco earthquake of 1906, by comparison, was felt moderately over 6,000 square miles (16,000 km²).
Based on the effects of these earthquakes, it can be estimated that they had a magnitude of 8.0 on the Richter scale. As a result of the quakes, large areas sank into the earth, new lakes were formed (notably Reelfoot Lake, Tennessee), and the Mississippi River changed its course, creating numerous geographic exclaves, including Kentucky Bend, along the state boundaries defined by the river.
Some sections of the Mississippi River appeared to run backward for a short time. Sandblows were common throughout the area, and their effects can still be seen from the air in cultivated fields. Church bells were reported to ring in Boston, Massachusetts and sidewalks were reported to have been cracked and broken in Washington, D.C..[1]
Almost 200 years after the earthquakes in 1811 and 1812, the course of the Mississippi River as it was before the events is still visible in the landscape of the affected areas today. Along and parallel to the Tennessee/Arkansas state line, the shrunken riverbed is still present.
The old riverbed, however, still defines state lines along the river, resulting in numerous small jogs where the borders divert away from the river and incorporate small exclaves of land on the opposite side of the river from the rest of their state.
Such exclaves include the Kentucky Bend, a part of Kentucky whose only land boundary is with Tennessee, and the town of Reverie, Tennessee, which lies on the Arkansas side of the river. - http://en.wikipedia.org/wiki/New_Madrid_Earthquake
Posts: 16662 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
The April 18, 2008 Midwest Earthquake was one of the largest earthquakes ever recorded in the state of Illinois, measuring at a magnitude of 5.2.[1] It occurred at 4:37am (5:37 EDT) along the Wabash Fault at a depth of 11.6 km. It was centered near West Salem, Illinois and Bellmont, Illinois, specifically 38.450°N, 87.890°W, [2] and felt as far as 450 miles (724 km) away.[3] Tremors were felt in Chicago[4], St. Louis[5], Indianapolis[6], Peoria[7], eastern South Dakota, Lexington[8], Cedar Rapids, IA[9], Atlanta[10], Kansas City[11], Cincinnati, Milwaukee, Des Moines,[3] Nashville,[12] and Louisville.
The earthquake was part of the Wabash Valley Seismic Zone, separate from the more famous New Madrid Seismic Zone. The Wabash Fault is an extension of the New Madrid Fault. [13]
A couple of weeks ago The History Channel ran a documentary on the New Madrid fault...its past activity, and speculation as to what damage the "Big One" might cause in the future. They were talking in terms of + 8.0.
The zone remains active today. In recent decades minor earthquakes have continued.[1] New forecasts estimate a 7 to 10 percent chance, in the next 50 years, of a repeat of a major earthquake like those that occurred in 1811-1812, which likely had magnitudes of between 7.5 and 8.0. There is a 25 to 40 percent chance, in a 50-year time span, of a magnitude 6.0 or greater earthquake.[2] - http://en.wikipedia.org/wiki/New_Madrid_Earthquake
Posts: 16662 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
Nor is the Southeast immune! There was a small quake here, near Winston-Salem NC a couple of years ago. The largest to hit the Southeast was the Charleston SC Earthquake of 1886. The historic buildings of Charleston all have earthquake bolts and there are seismic considerations in building design.
Posts: 7623 | Location: in the backwoods of North Carolina | Registered: 06-07-02
(CNN) -- A 4.5-magnitude earthquake shook southern Illinois early Monday, the latest in a string of quakes that have rattled the region since last week, according to the U.S. Geological Survey.
The quake -- the 18th since a magnitude 5.2 hit the area Friday morning -- was centered about six miles below ground and about 37 miles (60 km) north-northwest of Evansville, Indiana, or about 131 miles (211 km) east of St. Louis.
It struck at 12:38 a.m. local time (1:38 a.m. ET). There were no immediate reports of damage. - CNN
Note that this morning's quaake, which I felt, was the 18th since Friday's 5.4 quake. I have felt most of those 18, but didn't see any reference to them in the online news. Most were merely a second or two long. This morning's quake, however, was about 10 seconds or so.
I have a feeling that there are more to come. I have to wonder if these quakes are affecting the New Madrid fault line. The damage area for the New Madrid line is much larger, and a quake there could be catastrophic. Climatologist Iben Browning projected an increased risk of a major earthquake on the New Madrid Fault around December 2nd and 3rd, 1990. No noticeable seismic activity was recorded in that area on those dates. He was, apparently, 6300+ days early. However, it should be noted that he had warned of the deadly and devastating 1989 San Francisco earthquake a week before it hit. He also is credited with predicting the volcanic eruption of Mount St. Helens in 1980
Posts: 16662 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
Did you feel that? 3.7 aftershock rattles the region
05:52 PM CDT on Friday, April 25, 2008
(KMOV) – The U. S. Geological Service confirms that a strong aftershock shook the Midwest Friday afternoon. The 3.7 tremor hit at 12:31 and was centered just outside of Mt. Carmel, Illinois and about 207 miles from St. Louis.
This one I thought was a truck on the highway. I really do think that there is another quake coming that will top this. There seem to be too many in a few places, and the New Madrid fault has yet to be heard from.
Posts: 16662 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
RENO, Nev. -- Scientists at the University of Nevada, Reno are scrutinizing seismic readings and studying damage at residents' homes to try to figure out what's happening beneath the earth's surface under a northwest Reno neighborhood rocked by a seemingly endless string of earthquakes.
What they can't say is whether the hundreds of temblors that have rattled the area for two months -- the largest a magnitude 4.7 Friday night -- are subsiding or a prelude to bigger things to come.
"You're not going to get an earthquake prediction today," John Anderson, director of Seismology Laboratory at the University of Nevada, Reno, said Tuesday during a briefing with Gov. Jim Gibbons and emergency managers on the seismic activity.
Scientists are calling the swarm of temblors that began Feb. 28 the "Mogul earthquake sequence", in reference to the neighborhood where hundreds of mostly minor earthquakes have occurred.
But the shaking is unusual, seismologists say, because the intensity of the quakes has increased over the past few weeks. Generally, earthquakes tend to occur and are followed by smaller aftershocks.
Up until April 15, sizable quakes that could be felt were occurring about once every third day.
Then, the rate increased, with about three, 2.0 or larger incidents occurring daily.
On April 24, when the first 4.2 quake was registered, "all of a sudden we were seeing 20 (of the magnitude) 2s and larger per day," said state geologist Jon Price.
"This is an exceptionally vigorous sequence of earthquakes," Price said.
During the past week alone, more than 500 occurrences have been recorded.
Posts: 16662 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
ST. LOUIS - A small earthquake shook the St. Louis area Monday, causing some residents to awake to a disconcerting rumbling for the second time in less than a month.
There were no reports of damage or injuries.
The epicenter of the quake at 6:25 a.m. was in southwest St. Louis County — just the sixth documented earthquake over the last two centuries centered in St. Louis or the county. The U.S. Geological Survey estimated its magnitude at 2.7. Seismologists at Saint Louis University believe it was a 2.8 or a 2.9. - MSNBC
I really think there is more to come. The epicenter of this one is not near the New Madrid fault line or the Wabash Valley fault line.
Posts: 16662 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
I really think there is more to come. The epicenter of this one is not near the New Madrid fault line or the Wabash Valley fault line.
Of course there will be more; there will be earthquakes in that region for thousands upon thousands of years.
Another large earthquake in your region is inevitable. My only hope is that the epicenter of the next Midwestern “Big One” is a good distance from the heavily populated areas.
A few miles could drastically cut down the number of people that will be killed or injured, not to mention the property damage.
Earthquakes don’t necessarily follow “fault lines”, especially in the Midwest. Expanding salt deposits are much more of a factor than the fault lines.
Posts: 3621 | Location: Long Island, New York USA | Registered: 06-03-02
