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Posted at 10:58 AM ET, 02/07/2012

Bicentennial of the New Madrid earthquake sequence: Can it happen again?


New Madrid seismic zone
This winter is the bicentennial (200th) anniversary of the New Madrid, Missouri earthquakes, a series of the most powerful earthquakes to strike the eastern U.S. in recorded history. Three of the quakes in the series are estimated to have reached a magnitude between 7.0 and 8.0. The first earthquake occurred on December 16, 1811, the second on January 23, 1812, and the third on February 7, 1812 - exactly 200 years ago to date.

New Madrid was the closest settlement to the epicenters of the immense tremors. According to eyewitness accounts it was totally destroyed. At the time, most of the region, including many of the larger cities such as St. Louis were only sparsely populated with few permanent structures. Consequently, deaths and damages were limited.

Should a comparable sequence of earthquakes occur now, it would have consequences above and beyond any natural disaster the U.S. has ever experienced (and not in a sci-fi movie!).

Anyone in mid-Atlantic region on August 23 last summer no doubt remembers the largest Virginia earthquake in more than a century to shake the region, including Washington, D.C. Fortunately, the earthquake caused little in the way of serious injuries and overall did little damage (relative to 2011’s billion-dollar weather disasters) - not withstanding damage to the Washington Monument and Washington’s National Cathedral.

As a vast majority of the population had likely never having experienced a quake, it’s probably safe to say it threw a heart pounding scare into most. Not to mention, it came as a total surprise in a region generally believed to be earthquake free. (This most assuredly applies to me having been very close to the epicenter, as described here.)

By comparison, the three New Madrid 8.0 earthquakes were 158.5 times bigger than the 5.8 quake in August and almost 2000 times stronger in terms of total energy released. Indeed, each was comparable in strength to the devastating 1906 San Francisco earthquake remembered as one of the worst natural disasters in U.S. history.

Importantly, unlike the San Francisco earthquake and most large magnitude devastating events since (e.g., Alaska, 1906; 2011 Tohoku, Japan), the New Madrid (and Virginia) earthquakes did not occur along the Pacific Ring of Fire where Earth’s tectonic plates come together. Rather, the New Madrid seismic zone (series of faults) lies within a continental plate. Consequently, because of differences in the underlying geology, each of the largest Madrid quakes dangerously shook a much larger area than, for example, the Alaskan and San Francisco quakes (2–3 times and 10 times as large, respectively). The same can be said of the hundreds of aftershocks during the following decade, many of which were themselves respectable earthquakes (magnitude 5-6).

The Madrid quakes were felt across much of what is now the eastern U.S. - up to about 900 miles from the epicenters and reportedly strong enough to awaken sleepers in Washington, D.C, including on one occasion President Madison in the White House. Stone walls cracked in St. Louis. Church bells rang out in Charleston. However, the range of potentially damaging tremors appears to have been largely restricted to within about 300 miles of the epicenter.

An eyewitness somewhere within that 300 mile zone reported: “A rumbling noise was heard in the west and in an instant the earth began to totter and shake so that no persons were able to stand or walk. This lasted a minute; then the earth was observed to rolling in waves of a few feet in height, with a visible depression between.”

Other reports from diaries and local newspapers speak of:

* deep fissures and crevices some twelve feet wide and deep, and more than twenty feet in length

* some ground areas rising and falling as much as twenty feet causing the Mississippi River to run backwards

* huge waves of fifteen to twenty feet on the Mississippi River capsized boats and cargoes while leaving crews never seen again

* the atmosphere so choked with dust and smoke that for weeks afterward the sun shone reddish-bronze through an ugly haze.

* massive landslides along the Mississippi and Ohio River bluffs from Memphis to Indiana

All in all, for the relatively few settlers in the areas it must have been a dreadful experience marked by seemingly endless days and nights of earth-shattering aftershocks (hundreds)


Earthquake hazard map. (USGS)
The New Madrid seismic zone remains the most seismically active region and, hence, the highest earthquake risk within the continental U.S. outside California. Damaging tremors are not as frequent as in California, but when they occur, the destruction can affect a much larger area (as mentioned above).

According to the U.S. Geological Survey (USGS) a damaging earthquake in this area (magnitude 6.0 or so, comparable to the August quake in Virginia) occurs about every 80 years. The last one in was in 1895, so it appears one is well overdue. Some sources place the odds at 90% of such an event before 2040, but the USGS odds range from 28% to 46%.

A major earthquake, 7.5 or greater in the region, is projected to occur every 200- 300 years (the last one in 1812). USGS estimates there is a 20% chance of such an occurrence by 2040. (Note: these odds are acknowledged to be extremely uncertain given state of knowledge).

Quakes comparable to those during the 1811 to 1812 winter would affect just about half the U.S. with sizable damage and potential for significant loss of life spread through 20 states or more. Given the orders of magnitude increases in population, buildings of all kinds, and societal dependent infrastructure (e.g., communications, power, pipe lines, etc) since 1812, the level of damage, number of casualties, and degree of hardships are virtually beyond comprehension.

Congress allocated the equivalent of $833,000 for recovery in 1815; today it most certainly would be at least in the hundreds of billions of dollars and require several years at best for recovery. And that assumes the nation is (will be) prepared should such an event become a reality.

In May of 2011, the Federal Emergency Management Agency (FEMA) ran a White House mandated exercise, referred to as the National Level Exercise 2011 (NLE 11), simulating the response to the equivalent of the 1811/1812 New Madrid earthquakes. The purpose was to evaluate the nation’s catastrophic event preparedness by assessing the capabilities for multijurisdictional, integrated response to a national catastrophic event. The exercise included participants from various federal, state, and local agencies, as well as private sector and nonprofit organizations.

Among the preliminary results:

* developed and successfully exercised catastrophic event plans, including pre-scripted response checklists and catastrophic earthquake response

* demonstrated value of collaboration between government agencies and wide range of private sector and non-governmental partners

* initiated “forward-leaning” discussions regarding future planning and recovery within the initial response (72 hour) period

* drew attention to areas requiring further improvement within government agencies (not publically available)

Just days after the FEMA May 2011 completion of the simulated earthquake disaster, focus shifted to a real world operation in response to the May 22, 2011 deadly tornado striking Joplin, Mo. Officials reported that their participation in the simulation exercise directly contributed to an increased capability of the state and FEMA in responding in an effective, organized manner. But, an event not even close in magnitude to a repeat of New Madrid.

Bottom line: FEMA remains concerned about a Midwest earthquake producing mass casualties, tremendous economic aftershocks, and untold personal hardships of individuals and communities. It warns that it will come with virtually no warning.

New Madrid Bicentennial events: Organizations from across the U. S. will participate in observing the bicentennial of the great 1811 and 1812 New Madrid earthquakes. They range from conferences, workshops, public outreach events, multi-state earthquake exercises, field trips, and more. Organizers of the New Madrid Bicentennial events are planning the following activities:

2012 Earthquake Awareness Month - Throughout February 2012
Great Central U.S. ShakeOut - February 7, 2012 @ 10:15a.m.
2012 National Earthquake Conference and EERI Annual Meeting - April 10-14, 2012
St. Jude Dream Home Partnership - April 2012

Related links:

When will the Virginia earthquake aftershocks end?
Could a tsunami strike the U.S. East Coast?

By  |  10:58 AM ET, 02/07/2012

Categories:  Latest, Environment, Tracton

 
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