Spectrum - Volume 19 Issue 32 June 5, 1997 - Giles earthquake fertile subject

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Giles earthquake fertile subject
for Tech geological investigators

By Sally Harris

Spectrum Volume 19 Issue 32 - June 5, 1997

One hundred years ago on May 31, the earth shook violently in Giles County and throughout Virginia.
That date marks the centennial of the Giles County earthquake, the largest in intensity and area in Virginia in historical times and the third largest in the East in the last 200 years, according to Arthur Snoke of Virginia Tech's Geological Sciences Department, which houses the Virginia Tech Seismological Observatory.
The Giles earthquake had a maximum intensity of VIII on the Modified Mercalli Intensity Scale, and the region of maximum ground shaking extended over an elliptical area from Lynchburg west to Bluefield, W.Va., and from Giles County south to Bristol, Tenn. (The intensity assigned to an earthquake is based on human perceptions and the quake's effects on structures at a particular place, such as "many downed chimneys" and "changes in the flow of springs." The intensity varies with location.) The magnitude of the quake was judged to be about 5.8 on the more recent Richter scale
The shock of the Giles earthquake was felt severely at Narrows west of Pearisburg, where "the surface rolled in an undulating motion, water in springs became muddy, and water in some springs ceased to flow." Spring water flow was disturbed in the Pearisburg area and in Sugar Run.
The shock was strong at Pearisburg, where walls of old brick houses were cracked and many chimneys were thrown down or badly damaged. Chimneys were disturbed in areas ranging from Bedford to Bristol, and the earthquake was felt from Georgia to Pennsylvania and from the Atlantic Coast westward to Indiana and Kentucky. Aftershocks continued through June 6.
The Virginia Tech Seismological Observatory has put information on the World Wide Web concerning the Giles County and other earthquakes, including the often-conflicting news reports that abounded at the time. For example, Angels Rest, a high mountain near Pearisburg, was first reported cracked by the earthquake; but later reports denied that occurrence. From Saltville, a telegram came denying that the saltwells had gone dry since the earthquake shock.
In Richmond, "the vibrations lasted for several seconds and were so violent that many people ran out of their homes, fearing their collapse." Winston, N.C., reported "the most severe earthquake of any experienced in this section since the memorable Charleston earthquake in 1886," which had an estimated magnitude of 7.
The Virginia Tech Seismological Observatory, located on campus, conducts seismic-network operations that are part of a cooperative effort to monitor seismicity in the southern Appalachian region. The Virginia Tech Seismological Observatory operates a fully calibrated, digitally recording seismic network with stations in Virginia and southern West Virginia.
To access information about the Giles earthquake and others, as well as information about the Seismological Observatory and links to other seismological sites, visit site http://www.geol.vt.edu/outreach/vtso/vtso.html.