Big Earthquakes Not Unheard of in Eastern US

While today’s Virginia earthquake came as a surprise to most of us, earthquakes in the eastern United States are not unusual and can also be very destructive. According to the U. S. Geological Survey,  a series of earthquakes in New Madrid, Missouri exceeded the power of the Great San Francisco Earthquake by a factor of ten times.

Before today’s 5.9 Virginia earthquake, Virginia’s largest shake was a 5.9 temblor centered in Giles County  in 1897. That quake, much like today’s, was felt in 12 states, according to the U.S. Geological Survey. According to the USGS website, the largest damaging earthquake in the Virginia  central  seismic regional occurred in 1875 at magnitude 4.8.

According to the USGS, the Commonwealth  has had over 160 earthquakes over the past thirty years but only about 30 of the quakes were felt by humans. Today’s relatively mild shake appears to have been strong enough to disrupt two nuclear reactors located on nearby Lake Anna. Even so, larger quakes have occurred east of the Mississippi River.

The Charleston Earthquake of 1886 was a powerful intraplate earthquake that hit the area of Charleston, South Carolina. After the 1811 and 1812 quakes in New Madrid, Missouri, it is one of the most powerful and damaging quakes to hit the southeastern United States.

Source: US Geological Survey

Eyewitness accounts reported that shaking began occurring at 9:50 p.m. on August 31, 1886 and lasted just under a minute according to the USGS. The earthquake caused severe damage in Charleston, South Carolina, damaging 2,000 buildings and causing $6 million worth in damages (over $141 million in 2009 dollars), while in the whole city the buildings were only valued at approximately $24 million.

Between 60 and 110 lives were lost. Some of the damage is still seen today.

Major damage from the Charleston quake occurred as far away as Tybee Island, Georgia,- over 60 miles away – and structural damage was reported several hundred miles from Charleston including central Alabama, central Ohio, eastern Kentucky, southern Virginia and western West Virginia. The quake was felt as far away as Boston to the north, Chicago and Milwaukee to the northwest, as far west as New Orleans, as far south as Cuba, and as far east as Bermuda.

The earthquake is estimated to have been between 6.6 and 7.3 on the Richter scale.  Surprisingly, perhaps, very little to no historical earthquake activity occurred in the Charleston area prior to the 1886 event, which is unusual for any seismic area. USGS says that this lack of activity may have contributed to the severity of the tremor.

However, the power of the Charleston quake was dwarfed by the power of a series of quakes that hit New Madrid, Missouri over a period of three years beginning in 1811.

The sequence of three very large earthquakes is usually referred to as the New Madrid earthquakes, after the Missouri town that was the largest settlement on the Mississippi River between St. Louis, Missouri and Natchez, Mississippi.

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 New Madrid earthquakes of 1811-1812 rank as some of the largest in the United States since its settlement by Europeans says the USGS.

According to the USGS, the New Madrid quakes were by far the largest east of the Rocky Mountains in the U.S. and Canada. The area of strong shaking associated with these shocks is two to three times as large as that of the 1964 Alaska earthquake and 10 times as large as that of the 1906 San Francisco earthquake.

Because there were no seismographs in North America at that time, and very few people in the New Madrid region, the estimated magnitudes of this series of earthquakes vary considerably and depend on modern researchers’ interpretations of journals, newspaper reports, and other accounts of the ground shaking and damage.

The earthquakes caused the ground to rise and fall – bending the trees until their branches intertwined and opening deep cracks in the ground. Deep seated landslides occurred along the steeper bluffs and hillslides; large areas of land were uplifted permanently; and still larger areas sank and were covered with water that erupted through fissures or craterlets. Huge waves on the Mississippi River overwhelmed many boats and washed others high onto the shore.

The quakes caused high banks to cave and collapse into the river; sand bars and points of islands gave way; whole islands disappeared.

According to one eyewitness near New Madrid;

“At first the Mississippi seemed to recede from its banks, and its waters gathering up like a mountain, leaving for the moment many boats, which were here on their way to New Orleans, on bare sand, in which time the poor sailors made their escape from them. It then rising fifteen to twenty feet perpendicularly, and expanding, as it were, at the same moment, the banks were overflowed with the retrogade current, rapid as a torrent – the boats which before had been left on the sand were now torn from their moorings, and suddenly driven up a little creek, at the mouth of which they laid, to the distance in some instances, of nearly a quarter of a mile. The river falling immediately, as rapid as it had risen, receded in its banks again with such violence, that it took with it whole groves of young cotton-wood trees, which ledged its borders. They were broken off which such regularity, in some instances, that persons who had not witnessed the fact, would be difficultly persuaded, that is has not been the work of art. A great many fish were left on the banks, being unable to keep pace with the water. The river was literally covered with the wrecks of boats, and ’tis said that one was wrecked in which there was a lady and six children, all of whom were lost” recounted Eliza Bryan in “Lorenzo Dow’s Journal,” Published By Joshua Martin, in 1849.

Comments

  1. If the New Madrid Earthquake happened again today at the same intensity as 1811, it would be good bye St Louis, Missouri and Memphis, Tennessee. The energy released would cause a lot of damage and death. Fire burned San Francisco after the 1906 Earthquake along the San Andreas Fault. Bad things happen on Good Friday in Alaska. The 1964 earthquake and the 1989 Valdez oil spill started on Good Friday.