Why should people in the eastern U.S. be concerned about earthquakes?
1) Severe earthquakes have occurred in the Eastern U.S.:
In November of 1755, an earthquake with an estimated magnitude of 6.0 and a maximum intensity of VIII occurred about 50 miles northeast of Boston, Massachusetts. Boston was heavily damaged. Other strong earthquakes recorded in the continental US were centered in southeastern Missouri near the border with Arkansas, Kentucky and Tennessee. In the winter of 1811-1812, a series of three powerful earthquakes of magnitudes about 7.0 to 7.8 and hundreds of aftershocks occurred near New Madrid, Missouri. These shocks were so strong that observers reported that the land distorted into visible rolling waves. They changed the course of the Mississippi River, created a vast area of ground deformation and liquefaction features; and they were felt widely along the east coast of the U.S. 800 to 1000 miles away. Because the surrounding area was mostly undeveloped at the time, few deaths were reported and these events stirred relatively little attention then. In August of 1886, a strong earthquake occurred in Charleston, South Carolina. Magnitude is estimated at 6.8 to 7.2. Much of the city of Charleston was damaged or destroyed. Earthquakes in the East are not confined to these areas; they have been recorded in every State east of the Mississippi. Damaging earthquakes have occurred historically in nearly every eastern State.
2) Earthquakes of the same magnitude affect larger areas in the East than in the West:
The size of the geographic area affected by ground shaking depends on the magnitude of the earthquake and the rate at which the amplitudes of body and surface seismic waves decrease as distance from the causative fault increases. Comparison of the areas affected by the same Modified Mercalli intensity of ground shaking in the 1906 San Francisco, California, the 1971 San Fernando, California, the 1811-12 New Madrid, Missouri, and the 1886 Charleston, South Carolina, earthquakes shows that a given intensity of ground shaking extends over a much larger area in the Eastern United States. Ground shaking affects a larger area because amplitudes of seismic waves decrease more slowly in the east than in the west as distance from the causative fault increases.
Eastern North America has older rocks, some of which formed hundreds of millions of years before those in the West. These older formations have been exposed to extreme pressures and temperatures, making them harder and often denser. Faults in these older rocks have also had more time to heal, which allows seismic waves to cross them more effectively when an earthquake occurs. In contrast, rocks in the West are younger and broken up by faults that are often younger and have had less time to heal. So when an earthquake occurs, more of the seismic wave energy is absorbed by the faults and the energy doesn’t spread as efficiently.
Why was an earthquake in Virginia felt at more than twice the distance than a similar-sized earthquake in California? The answer is one that many people may not realize. Earthquakes east of the Rocky Mountains can cause noticeable ground shaking at much farther distances than comparably-sized earthquakes in the West.
New Simulations of 1811-1812 New Madrid Earthquakes Show Strong and Prolonged Ground Shaking in Memphis and Little Rock
Computer simulations of earthquake shaking, replicating the quakes that occurred in 1811-1812 in the New Madrid seismic zone (NMSZ), indicate that future large earthquakes there would produce major, prolonged ground shaking.
Imagine the Delaware River abruptly rising toward Philadelphia in a tsunami-like wave of water. Scientists now propose that this might not be a hypothetical scenario. A newly published paper concludes that a modest (one-foot) tsunami-like event on the East Coast was generated in the past by a large offshore earthquake.
Virginia Earthquake Triggered Landslides at Great Distances
What if you knew that a magnitude 7.8 earthquake would happen in less than three weeks? In a new video interview, USGS earthquake scientist Dr. Lucy Jones explains that millions of Southern Californians will be preparing as if they do know, thanks to the Great Southern California ShakeOut.
Scientists from the U.S. Geological Survey (USGS) and the Center for Earthquake Research and Information at the University of Memphis have updated their expectations for earthquakes in the New Madrid Seismic Zone.
A minor earthquake, preliminary magnitude 3.7 according to the U.S. Geological Survey, occurred near Newcomb, New York at 4:47 am Eastern Daylight Time. The epicenter was about 95 miles north northwest of Albany. The earthquake was felt in Montpelier, VT and Springfield, MA. The USGS has received no reports of damage at this time.
A timeline of earthquakes in the New Madrid Seismic Zone (top) differs significantly from a typical aftershock sequence (bottom). A new study shows that earthquakes occurring today in the region are not aftershocks of the 1811-1812 earthquakes. Rather, they are evidence that stress is continuing to accumulate. Data source: CEUS-SSC catalog.
The Washington Monument, made of marble, granite, and bluestone gneiss, commemorates the first president of the United States. The monument was damaged in the 2011 Virginia earthquake, but has since been repaired.
A year after the August 23, 2011 Virginia earthquake, USGS geologist Dr. Mike Blanpied discusses whether a similar event could occur again in the region in the near future, and in an earthquake, what you can do to stay stay safe.
A year after the August 23, 2011 Virginia earthquake, USGS geologist Dr. Mike Blanpied discusses USGS efforts currently underway to learn more about the cause of the event. Dr. Blanpied discusses how scientists are using the August 23 earthquake to inform estimates of the region's seismic hazard.
The magnitude 5.8 earthquake that struck Louisa County was among the largest to occur along the eastern seaboard of the United States. It caused extensive damage in central Virginia and was likely felt by more people than any other earthquake in U.S. history. Join USGS scientists Mike Blanpied and Mark Carter on November 2nd to discuss the seismology of the earthquake, its...
USGS geologist Ed Harp photographing a small rock fall from a road cut along the Blue Ridge Parkway north of Roanoke, Virginia. This is part of a study documenting landslides triggered from the 2011 magnitude 5.8 earthquake in Virginia. Green grass beneath the rock fragments indicates that the rock fall is fresh and probably was triggered by the earthquake.
Photo of chimney damage at a house in Louisa County, Virginia. This was a result from a magnitude 5.8 earthquake in Virginia on August 23, 2011.
A magnitude 5.8 earthquake occurred in Virginia on August 23, 2011. Join us as we talk to David Russ, who is the USGS Regional Executive for the Northeast Area, about that event as well as earthquake risk, history and geology along the East coast.
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Damage to a house in Louisa County, Virginia, after a magnitude 5.8 earthquake on August 23, 2011.
Chimney damage to a house in Louisa County, Virginia, after a magnitude 5.8 earthquake on August 23, 2011.