Post by njc » June 17th, 2005, 8:29 am

I didn’t want to take over Libster’s thread checking in on those living in California, but I just love earthquakes and volcanoes and all the stuff that goes along with it. I was obsessed when I was in school studying this stuff, and I guess I still am!


I wrote in the previously mentioned thread about an earthquake that occurred in Virginia in 2003, the first one I have ever experienced. I had no clue what was going on, because as with most, I never thought about earthquakes occurring in the east, I always think of Cali and other locations along the “Ring of Fire”. Even with all my research in school, I always focused out there.


So I was looking around the internet trying to find a story about the earthquake in VA to post (http://fredericksburg.com/News/FLS/2003/122003/12092003/1193995) and came across some other things of interest about earthquakes and the southeast US…


Virginia, like most states on the eastern seaboard, has a moderate level of risk from earthquakes (see attached drawing). The largest earthquake known to have occurred in the region was the 1886 Charleston, South Carolina, earthquake (estimated magnitude 6.6-6.9). That quake was felt as far north as Canada, as far west as Missouri, and as far south as Cuba.


Since 1774, the year of the earliest documented Virginia earthquake, there have been over 300 earthquakes in or near the Commonwealth. The largest earthquake in Virginia was the 1897 Giles County shock (near Virginia Tech). The maximum intensity was VIII (Mercalli scale) in Giles County, and it was felt over 11 states (approximately 280,000 square miles). The estimated magnitude for this event was 5.8, making it the third largest earthquake in the eastern United States in the last 200 years (second largest in the southeastern U.S.).


Taken from http://www.mme.state.va.us/DMR/PUB/Brochures/quake.html

Image




In 1897, an earthquake with an estimated magnitude of 6.0 rocked Virginia Tech in the southwestern area of the state, Chapman said. The shock was centered in neighboring Giles County and was felt from Pennsylvania to Georgia. And although we tend to think of Alaska and California as the typical sites of seismic activity in the United States, eastern Tennessee is one of the most active areas in the nation in terms of the number of earthquakes recorded.
The most damaging seismic event in the U.S. prior to the 1906 earthquake and fire that destroyed San Francisco occurred in coastal South Carolina in 1886, Chapman said. The "Charleston earthquake," which caused structural damage as far away as Richmond and Atlanta, reached an estimated magnitude of 7.3 on the Richter scale -- essentially the same magnitude as the shock that killed more than 17,000 people in northwestern Turkey in August 1999.


"Recent seismological studies suggest that the southern Appalachian highlands have the potential for even larger earthquakes than have occurred in the past," Martin said. "But now those events would take place in much more highly populated areas. Felt earthquakes don't occur as often in the Southeast as in California, because the tectonic strain rates are different. Our region tends to experience large earthquakes isolated by long periods of quiet."


"However," James Martin warned, "we are under a significant threat of large, damaging earthquakes. In terms of seismic vulnerability, many buildings in the southeastern U.S. today are similar to those in Turkey. In neither place is there adequate structural protection of buildings. If another 7.3 magnitude earthquake hit Charleston today, the city would suffer much the same damage as cities in Turkey."


There's another difference between California and the Southeast as seismic zones. "The earth's crust is stronger here," Chapman explained. "So shock waves moving from the epicenter of an earthquake don't lose as much energy as during quakes in California. When a magnitude 7.0 earthquake occurs in the Southeast, the waves affect a larger area and can cause more damage at a greater distance than when a similar shock hits California."


Taken from http://www.sciencedaily.com/releases/2003/12/031212080152.htm


So anyways… thanks for letting me share this long post. I just find it so interesting! Image