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THE MINERAL, VIRGINIA EARTHQUAKE
Lessons From A Rare, Shallow-Depth, Moderate - Magnitude Event
in the Eastern United States
AUGUST 23, 2011
Dr. Walter Hays,
Global Alliance For Disaster Reduction
Earthquakes are rare in the Eastern U.S. because the region is several hundred
miles away from the closest plate boundary, which is in the middle of the Atlantic Ocean.
Today’s shallow (1 km) earthquake was probably
generated by rupture of the Spotsylvania fault, an
ancient break in the Earth’s crust that is now a part of the North American plate.
THE M5.8 EARTHQUAKE OCCURRED AT 1:51 PM ON
AUGUST 23rd
THE M5.8 EARTHQUAKE OCCURRED AT 1:51 PM ON
AUGUST 23rd
The USGS downgraded the magnitude from M5.9 (tied for largest historic
quake in Virginia) to M5.8
ALTHOUGH A MODERATE EARTHQUAKE, THIS
EARTHQUAKE WAS THE LARGEST IN VIRGINIA SINCE
1897
ALTHOUGH A MODERATE EARTHQUAKE, THIS
EARTHQUAKE WAS THE LARGEST IN VIRGINIA SINCE
1897
WHAT HAPPENED FOLLOWING TODAY’S MODERATE
EARTHQUAKE
WHAT HAPPENED FOLLOWING TODAY’S MODERATE
EARTHQUAKE
Above all else, it was a WAKE-UP call!!!
No deaths, but with typical short- period effects close to the source and long-
period effects far from the source
Although the epicenter of the quake (and the source of the
seismic energy) was in Mineral, VA, the ground shaking was felt
as far north as Boston, New York, and Detroit, and as far
south as Atlanta.
NOTE: The rocks in the Eastern United States are old and cold,
which makes them more efficient in transmitting seismic energy from a M5.8 quake much farther than the young and hot
rocks in the Western United States.
1. Be ready to protect your capitol, your community, your
school, your business, --- and your people.
2. Be prepared for an act of terrorism, which is what many people thought that
the earthquake was (i.e., in some unknown way another
9/11 act of terrorism).
3. Be prepared for what can happen in a rare event---a moderate
earthquake that only happens every
century--- that can impact one-half of the
nation.
4. Be prepared for the situation when local
communication is disrupted and even shut down (i.e., when cell phones and the internet become useless immediately after a major
earthquake occurs).