New Madrid Seismic Zone
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New Madrid - Witness to the Event
What if the 1811 New Madrid M8 earthquake occurred in 1821? 1950? 2000?
The population of the New Madrid region was sparse in 1811, but the shaking was felt as far as Boston. This rollover map superimposes the intensity isolines (isopleths) on a conterminous U.S. map. Scroll over the timeline on the bottom to watch the population increase. (Maps from Colorado State University)
Flash (671 kB)
What did the pioneers to Missouri witness? Although population was sparse in the region, the pioneers settling there wrote astounding reports of thousands of acres of forest devastation, land upheaval, and the Mississippi River briefly running backwards. The rollover offers extracts from diaries and newspaper articles.
Flash (1.29 MB)
How can a river run backwards?
This animation, also embedded in the rollover, shows how a river can be forced backwards, albeit only long enough to find a new route. Several written accounts describe the horror as great waters swashed upriver causing lakes to form on previously dry land.
Quicktime (2.35 MB)
New Madrid - Geology and Geologic History
Volcanoes, dinosaurs & inland sea around New Madrid?
There is an interesting geologic story told in the rocks of the New Madrid seismic zone. This animation takes each segment of geology and spins a scenario in cross section to see how the landscape has changed over its 500 million year history.
Quicktime (4.46 MB)
This rollover shows various regional geologic components of the broader New Madrid seismic zone (NMSZ), including age of the rocks, historic seismicity, faulting, hotspot (really?!), and how did New Madrid get from an ancient equatorial landscape to where it is today?
Flash (1.15 MB)
This animation (embedded in the geology rollover) illustrates a 500 million year history of continental breakup and migration of the North American continent, with a star indicating the location of NMSZ rocks through time.
Quicktime (1.58 MB)
New Madrid - Seismology & Paleoseismology
How do we know there were big earthquakes in the New Madrid region before 1811?
First look at the map of seismicity between 1974 and 2010; the activity is ongoing. By studying the geologic history recorded in rock & sediment layers, paleoseismologists and geologists have learned that large earthquakes can occur every 400–600 years. The most important clues include evidence for liquefaction.
Flash (657 kB)
What is the evidence for Liquefaction?
The sand-blow photo shows an actual outcrop excavated by paleoseismologists. These scientists understand how liquefaction works and what to look for in the landscape to determine the age of the features. (To learn about sand blows (aka "sand boil") watch the animation)
Flash (113 kB)
Present-day earthquake activity falls on faults that reflect past earth movement. This rollover shows recent earthquakes as well as the location of the large earthquakes of 1811–1812 and briefly describes the subsurface structures revealed by seismologists.
Flash (193 kB)
Can you see a fault in the data?
Touch "Raw data used" first. Seismologists collect data as sound and seismic waves are transmitted through the Earth and reduce the data to "squiggles". They interpret the images to see changes in rock layers at depth. A map on "Why did we do it?" shows the range of earthquakes since 1811 and tells why we bother to do seismic soundings.
Flash (760 kB)
The animation shows how sound waves, emitted by an energy source towed beneath a boat, are recorded and interpreted by seismologists.
Quicktime (4.83 MB)
How does charcoal tell us about pre-historic earthquakes?
Over the past decade paleoseismic studies have begun to unravel the fascinating earthquake history of the New Madrid seismic zone. Rollover the color bars to see the evidence for past earthquakes.
Flash (1.78 MB)
Animations and videos are made in partnership with Earthscope, USGS, and Volcano Video & Graphics.
Please send feedback to Jenda Johnson.