New Madrid Earthquake Sequence Dec 1811–Feb 1812


by Astronuc
Tags: 1811–feb, 1812, earthquake, madrid, sequence
Astronuc
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Nov7-11, 06:43 PM
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We're approaching the bicentennial anniversary of the largest earthquake and swarm east of the Rocky Mountains, at least in recent history. Coincidentally, Oklahoma has just had it's largest earthquake in the state's history.

Bicentennial of the New Madrid Earthquake Sequence December 1811–February 1812

http://pubs.usgs.gov/gip/134/

The page and posters summarize a few of the more significant facts about the series of large earthquakes that struck the New Madrid seismic zone of southeastern Missouri, northeastern Arkansas, and adjacent parts of Tennessee and Kentucky from December 1811 to February 1812. Three earthquakes in this sequence had a magnitude (M) of 7.0 or greater. The first earthquake occurred on December 16, 1811, at 2:15 a.m.; the second on January 23, 1812, at 9 a.m.; and the third on February 7, 1812, at 3:45 a.m. These three earthquakes were among the largest to strike North America since European settlement. The mainshocks were followed by many hundreds of aftershocks that occurred over the next decade. Many of the aftershocks were major earthquakes themselves. The area that was strongly shaken by the three main shocks was 2–3 times as large as the strongly shaken area of the 1964 M9.2 Alaskan earthquake and 10 times as large as that of the 1906 M7.8 San Francisco earthquake. Geologic studies show that the 1811–1812 sequence was not an isolated event in the New Madrid region. The 1811–1812 New Madrid earthquake sequence was preceded by at least two other similar sequences in about A.D. 1450 and A.D. 900. Research also indicates that other large earthquakes have occurred in the region surrounding the main New Madrid seismicity trends in the past 5,000 years or so.

1. First Mainshock Earthquake
The first in a series of major earthquakes occurred on December 16, 1811, at about 2:15 a.m. near present-day Blytheville, Arkansas. Estimated at magnitude (M) 7.7 (footnote 1), this event awakened people across much of what is now the eastern United States, up to about 900 miles away, including President James Madison in Washington, D.C. There were several large aftershocks that day, including the largest “Dawn” aftershock at about 7:15 a.m., estimated at M6.8–7.0.

4. Second Mainshock Earthquake
The second of the three major earthquakes, estimated at M7.5, occurred on January 23, 1812, at about 9:15 a.m. Similar to the December 1811 earthquake, this event was also widely felt throughout the region. Damage occurred in an area of about 232,000 square miles.

7. Third Mainshock Earthquake
The third and probably the most widely felt of the three major New Madrid earthquakes occurred on February 7, 1812, at about 3:00 a.m. There were several destructive shocks that day, the last and largest estimated at M7.7. As a result, the town of New Madrid, Missouri, was severely damaged.
The seismic activity can abruptly and dramatically change anywhere in the world, as was witnessed in the Canterbury region around Christchurch, NZ on Sept 4, 2010, although one might expect such activity in that part of the world which sits astride the boundary of the Australia and Pacific plates.

The middle of the US has been considered stable, so strong earthquakes are rather surprising.

It will be interesting to see what follows the recent earthquakes in Va and Ok.
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davenn
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Nov7-11, 09:55 PM
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Quote Quote by Astronuc View Post

Big SNIP :)


The middle of the US has been considered stable, so strong earthquakes are rather surprising.
.
"Had been considered stable...." may be a better phrase ;)

My memories go back to my visit to the USGS office in Boulder, CO. in 1999. Talking to Dr Mark Meremonte and others there who had done/still doing (at that time) considerable research on the New Madrid Fault Zone. The zone is currently displaying thrust and strike-slip tectonics but appears to have undergone several cycles of extension and compression over geological history. It seems the area is what is termed a "Failed Continental Rift Zone".

Quite amazing really ... cuz if it has really developed I wonder how far north the rifting would have gone and what it would have looked like. Maybe a bit like the Gulf of California, which of course is extensional.

cheers
Dave
Evo
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Nov7-11, 10:15 PM
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There was a 4.2 aftershock about an hour ago.

davenn
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Nov7-11, 10:56 PM
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New Madrid Earthquake Sequence Dec 1811–Feb 1812


hi Evo


Quote Quote by Astronuc
It will be interesting to see what follows the recent earthquakes in Va and Ok.
haha ... you spoke it into being mate ;)


Magnitude Mb 4.7

Date-Time
Tuesday, November 08, 2011 at 02:46:57 UTC
Monday, November 07, 2011 at 08:46:57 PM at epicenter

Location
35.541°N, 96.754°W

Depth
5 km (3.1 miles)

Region
OKLAHOMA

Distances
28 km (17 miles) NNE of Shawnee, Oklahoma
69 km (42 miles) SSE of Stillwater, Oklahoma
70 km (43 miles) E of OKLAHOMA CITY, Oklahoma
71 km (44 miles) ESE of Guthrie, Oklahoma

USGS

This has really been the year for significant events outside of the western states (CA,OR,WA)
much more activity than in recent years
Dave
Evo
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Nov7-11, 11:01 PM
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Thanks Dave!
davenn
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Nov8-11, 02:50 AM
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well I didnt record that one far too far and too small.
But I did record the Mw6.9 NE of Taiwan that occurred shortly after the OK event

cheers
Dave
DrClapeyron
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Nov24-11, 02:19 PM
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It also sits right in between the base of the Appalachian Mountains and the Interior Highlands/Ouchita buried mountain belt. I know the Appalachian Mts. are linked to the break of a super continent, and the burried Ouchita Mts. (Oklahoma and Texas) and the Interior highlands of Arkansas are related to the opening of the Gulf of Mexico.

However I have heard that the two could be related. Could the Mississippi rift be a result of these two events?


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