Vol. 91
No. 2
June 2015
An Earthquake History:
Finding Faults in Virginia
by Wendy S. Kelly and Anne C. Witt
Introduction
Each year, hundreds of lives are lost and billions
of dollars in damages occur in the United States
due to natural hazards.1 While geological hazards
like earthquakes, tsunamis, and volcanic eruptions
account for only 10 percent of the monetary losses
from all types of natural hazards, their impacts can
be catastrophic and economically overwhelming to
individual communities.1 Unlike hurricanes and
floods, where we may have days of warning and
preparation time, earthquakes are unpredictable
and can occur without warning at any time of the
year.
When a 5.8 magnitude earthquake shocked
central Virginia in August of 2011, it drew new
attention to seismic hazard preparedness in what
are commonly considered less seismically active
areas of the United States. Although most people
would not consider earthquakes a common occurrence in Virginia, small earthquakes have occurred
regularly throughout recorded history and will
continue to occur into the future. Earthquakes
will pose an even greater risk as population density
and development continue to increase. Developing
resources to improve our understanding of earthquake dynamics, frequency, and intensity will ultimately improve our ability to mitigate losses from
earthquake hazards and may eventually lead to
earthquake prediction.
In response to the 2011 Virginia earthquake,
the Federal Emergency Management Agency
Wendy S. Kelly
(FEMA) issued a major disaster declaration to offer
assistance to affected businesses and residents. The
Virginia Department of Emergency Management
(VDEM) is currently managing hazard mitigation
projects related to the earthquake that are funded
by the FEMA Hazard Mitigation Grant Program.
The Virginia Department of Mines, Minerals, and
Energy (DMME) Division of Geology and Mineral Resources (DGMR) is completing one of these
projects, which involves evaluating Virginia’s seismic history and compiling a geodatabase of the
state’s geologic faults to help assess seismic hazards.
Anatomy of an Earthquake
Anne C. Witt
The Earth is dynamic. The tectonic plates that
make up the outer layer of the Earth are in constant motion. Stress from their motion transfers
across space and accumulates through time. When
a sudden release of accumulated stress occurs along
a geologic fault, an earthquake occurs (Figure 1).
An earthquake originates on a two-dimensional geological discontinuity called a fault. The
point at which the earthquake initiates is called the
hypocenter. Earthquake hypocenters can be located
relatively close to the Earth’s surface (down to 40
miles in depth) or very deep (hundreds of miles in
depth). Once an earthquake occurs, the released
energy propagates as seismic “body waves” away
from the hypocenter traveling through the Earth’s
crust. Body waves consist of compressive P-waves
The Virginia News Letter
Figure 1: Anatomy of an Earthquake
“Although the majority of earthquakes
are concentrated
along tectonic plate
boundaries, earthquakes can also occur
along faults within
the interior of tectonic plates, such as
in eastern
North America.”
Source: Modified from the U.S. Geological survey (USGS).
http://earthquake.usgs.gov/learn/animations/
(primary waves) that travel at the speed of sound,
and the slower moving, but more destructive,
S-waves (secondary waves) that move with a
shearing motion. Once these seismic waves reach
the Earth’s surface, they travel as surface waves
away from the epicenter, the location of the hypocenter projected upwards to the ground surface.
Like body waves, surface waves vary in motion.
Rayleigh waves roll across the Earth’s surface,
whereas Love waves move horizontally. Both
types of surface waves are potentially destructive.
Earthquakes are measured by the amount
of energy they release (magnitude) and by the
amount of damage they cause (intensity) (Table 1).
The magnitude of an earthquake can be measured
by instruments called seismometers. Each seismic event has a single measure of magnitude.
The intensity of an earthquake is the amount of
shaking an earthquake produces, which may rattle
dishes, overturn furniture, and damage buildings. Because seismic waves dissipate, intensity
decreases as distance from the epicenter increases;
therefore multiple measurements of intensity can
result from a single earthquake.
The majority of earthquakes occur where
tectonic plates meet and grind together—here
stress is the greatest. An example is the April
2015 Nepal earthquake, which occurred along
an active plate boundary where the Indian Plate
is sliding beneath the Eurasian Plate. Similarly,
eastern Japan and the western United States are
active tectonic settings with a high incidence of
seismicity. Although the majority of earthquakes
are concentrated along tectonic plate boundaries,
earthquakes can also occur along faults within
the interior of tectonic plates, such as in eastern
North America. (Figure 2)
Human Activity and Earthquakes
Although earthquakes are naturally occurring
geologic events, they can also be triggered by
human activity. Such induced, or “anthropogenic seismicity,” may occur as human industrial
activity related to deep well injection, mining, or
reservoir construction, alter stresses within the
Earth’s crust.2
Table 1: Earthquake Magnitude and Typical Correlated Intensity
2
Source: Modified from the U.S. Geological Survey (http://earthquake.usgs.gov/learn/topics/mag_vs_int.php and http://pubs.usgs.gov/gip/
earthq4/severitygip.html)
Weldon Cooper Center for Public Service • June 2015
Figure 2: The Worldwide Prevalence of Earthquakes
“To date, no
Virginia earthquakes have been
attributed to oil
and gas activity.”
Note, black and red dots illustrate global earthquake concentration.
Source: Reproduced by permission of the British Geological Survey. © NERC. All rights reserved. CP15/024.
http://www.bgs.ac.uk/discoveringGeology/hazards/earthquakes/whyWhere.html.
During oil and natural gas production, fluids may be removed or injected underground.
This activity can cause stresses within the Earth’s
crust to change, potentially triggering earthquakes. For example, a magnitude 6.5 earthquake in California in 1983 and a magnitude
7.0 earthquake in Uzbekistan in 1984 have been
attributed to oil and gas production.2 The modern technique of hydraulic fracturing to stimulate deep underground oil and gas reservoirs has
been associated with the increase of seismicity
in the central U.S.3, but this increase has been
primarily attributed to the injection of oilfield
wastewater into deep disposal wells. To date, no
Virginia earthquakes have been attributed to oil
and gas activity.
Mining can also cause seismicity. In areas
where coal is mined, such as the Appalachian
Basin of West Virginia, Kentucky, and far southwestern Virginia, underground voids left by the
removal of coal sometimes collapse, causing tremors. Rock blasting in the mining process can also
cause ground shaking. The tremors are detected by
seismometers in the region and often reported as
earthquakes, although their location and seismic
waveforms usually inform researchers that the
events are not natural.
“Reservoir-induced seismicity” is another
well-known phenomenon in which earthquakes
are triggered by the filling of large, man-made
water reservoirs. Although the mechanisms
by which these earthquakes occur are not well
understood, it is likely that the geologically
rapid loading of the earth’s crust from the
weight of water and the propagation of hydraulic forces into existing fracture systems combine
to release stress in the crust. Nearly 60 cases of
reservoirs causing earthquakes are documented
in the scientific literature.4 Some of these earthquakes, such as a magnitude 6.1 earthquake
that occurred in 1993 after the construction of
a water reservoir in southwestern India, can be
quite large.
Unraveling Virginia’s Seismic History
Although a great deal has been learned about
earthquakes in other portions of the globe,
much remains to be understood about seismicity
in the eastern United States. Far from a tectonic
plate boundary, Virginia rests within the geologically stable center of the North American
tectonic plate. Even so, earthquakes are nothing
new to Virginia. Hundreds of millions of years
of geological processes have shaped the commonwealth’s landscape. The same processes that
built the Appalachian Mountains and opened
the Atlantic Ocean have left Virginia laced with
geologic faults. Because these faults are locations of weaker crust, they potentially present
a path of least resistance for the Earth’s shifting tectonic plates. Even though generations
of geologists have mapped thousands of faults
across Virginia, many remain to be discovered.
Often, faults are “blind” or hidden underground
(see Figure 1). Without surface evidence, locating faults and attributing an earthquake to
motion along a particular fault can be challenging. Examining Virginia’s seismic history may
reveal trends in earthquake frequency and clustering, which may also help geologists determine
recurrence probabilities and identify potentially
active faults.
3
The Virginia News Letter
Prehistoric Earthquakes
“In general,
Virginians have
experienced
frequent, but low
magnitude seismic
events almost
every year.”
Today, scientists rely on technology to identify and
accurately record information about earthquakes.
Virginia’s first seismometer was installed in
Blacksburg in 1963, digitally recording local earth
tremors as part of a national monitoring system.
However prior to that date, our record of earthquakes is incomplete. Historical records, such as
newspapers and journals, are our best source for
information about past occurrences. Documenting earthquakes prior to colonization becomes
even more challenging. Although earthquakes
certainly occurred, humans may not have been
present to witness the events, or written records
may not have been kept. However, evidence for
prehistoric seismicity may be preserved within the
geologic record.
Earthquakes of a high enough magnitude
and intensity cannot only cause destruction on
the surface, but can also disrupt the subsurface
(Figure 3). Geologists can look for deformation
of soft sedimentary deposits or of hard geological features (such as breakdown of cavern formations). Although research is ongoing, these types
of deformation features have been identified
within the Piedmont Province of central Virginia and caverns of the Valley and Ridge Province. Such features, called paleoseismites, may be
measureable indicators of prehistoric earthquakes
occurring at least within the past 27,000 years of
geologic time.5,6,7
Figure 3: Illustration of Earthquake-induced
Deformation
Source: The Virginia Department of Mines, Minerals, and Energy
(DMME) Division of Geology and Mineral Resources (DGMR)
Historic Earthquakes
More recent seismic events have largely been captured by historical documents. Sources such as
newspapers and journals provide a record of hundreds of earthquakes occurring in Virginia over
the past few hundred years. In general, Virginians
have experienced frequent, but low magnitude
seismic events almost every year. The majority of
these earthquakes have caused little to no damage. Larger magnitude earthquakes have occurred
much less frequently, but stand out in documentation as memorable and occasionally damaging
(Figure 4).
The first earthquake recorded in Virginia history was documented by Thomas Jefferson. In the
afternoon of February 21, 1774, his Charlottesville
Figure 4: Magnitude of Historically Recorded Earthquakes in Virginia, 1774 to 2014
4
Note, magnitude increases as shading transitions from grey to red. Refer back to table 1 for more information about magnitude.
Source: The Virginia Department of Mines, Minerals, and Energy (DMME) Division of Geology and Mineral Resources (DGMR)
Weldon Cooper Center for Public Service • June 2015
Figure 5: Generalized Felt Area with Intensities for the February 21, 1774 Earthquake
“Many earthquakes
are preceded or
followed by a series
of more minor
earthquakes that
may cause just as
much damage as the
main shock.”
Source: Modified from M.G. Hopper, and G.A. Bollinger, The Earthquake History of Virginia, 1774 to 1900, Virginia Polytechnic Institute and
State University, Blacksburg, Va., 1971.
estate house, Monticello, was shaken so terribly
that the inhabitants are reported to have run outside in fear.8 People also ran outside in the towns
of Williamsburg and Fredericksburg, where buildings shook and glasses rattled.3 The first newspaper published in Virginia, The Virginia Gazette,
also recorded this event as being strongly felt in
Richmond and Westover, accompanied by a loud
thunderous sound.9
Aside from causing a general panic, the
1774 earthquake reportedly resulted in serious
structural damage close to the probable epicenter. In the towns of both Petersburg and nearby
Blandford, houses were physically dislodged from
their foundations.3,10 Store bells as far away as
Winston-Salem, North Carolina chimed.11 Even
though seismometers did not exist in the 1700s,
historic records of damage can help today’s geologists assign intensities and piece together a possible epicenter and magnitude for previous events.
Based on historic documents, people within
50,000 square miles of the 1774 earthquake
reported feeling the event, shocking individuals throughout much of Virginia and into North
Carolina (Figure 5). 2,12,13
One of Virginia’s largest earthquakes occurred
over a hundred years later in Giles County in
western Virginia on May 31, 1897. Newspaper
reports suggest that this event was felt over an area
of 300,000 square miles from Georgia to Pennsylvania and as far west as Indiana (Figure 6).14
This 5.8 magnitude event caused the greatest
damage in the towns of Narrows and Pearisburg,
which were closest to the epicenter. Brick homes
and chimneys were damaged (cracked, shifted,
or toppled) in a wide area around the epicenter
from Knoxville, Tennessee and Bluefield, West
Virginia to Raleigh, North Carolina.15 Springs
are reported to have been disturbed and landslides
triggered.16
Many earthquakes are preceded or followed
by a series of more minor earthquakes that may
cause just as much damage as the main shock.
Weeks before the 1897 event an intensity VII
foreshock caused plaster and chimney damage in
the towns of Radford, Pulaski, and Roanoke, and
was felt in several North Carolina towns.15,17 The
1897 main shock was also followed by a series of
aftershocks that lasted throughout the remainder
of the year.16 On June 28, an aftershock was felt
from Lexington to Wytheville, causing a general
disturbance and rattling kitchenware and windows in Roanoke.9 Another pronounced aftershock occurred in Pearisburg on September 3, and
a third in Wytheville on October 20.9 Although
none of these aftershocks caused significant
5
The Virginia News Letter
Figure 6: Generalized Felt Area with Intensities for the May 31, 1897 Earthquake
“...the most damaging earthquake ever
felt in Virginia’s
documented history
was recorded on
August 23, 2011.”
Source: Modified from M.G. Hopper, and G.A. Bollinger, The Earthquake History of Virginia, 1774 to 1900, Virginia Polytechnic Institute and
State University, Blacksburg, Va., 1971 and from S. E. Hough, “Initial Assessment of the intensity Distribution of the 2011 MW 5.8 Mineral,
Virginia Earthquake,” Seismological Research Letters, Vol. 83, No. 4, (2012) p. 649-57. http://pasadena.wr.usgs.gov/office/hough/649.full.pdf
damage, they were described in local newspapers
as “distinct.”
Modern Earthquakes
6
In modern times, networks of seismometers have
been installed across the eastern United States
to detect even the slightest of earthquakes. Such
highly sensitive seismic networks help scientists
accurately pinpoint earthquake epicenters and
measure magnitudes. In Virginia, several seismometers are recording Earth tremors and relaying the information back to universities and other
scientific facilities for analysis (Figure 7).
With the help of some of these devices, the
most damaging earthquake ever felt in Virginia’s
documented history was recorded on August
23, 2011. Approximately 150,000 individuals
reported feeling the earthquake through the U.S.
Geological Survey Earthquake Hazard Program,
“Did You Feel It?” website (http://earthquake.
usgs.gov/earthquakes/dyfi/). The earthquake was
felt over the entire eastern United States and into
Canada, potentially making it the most widely felt
earthquake in United States history (Figure 8).18
This 5.8 magnitude earthquake shocked residents of Central Virginia as homes were shifted
off of their foundations, chimneys toppled, and
house walls and framing cracked and buckled
(Figure 9). Total damages resulting from the
2011 earthquake reached at least $300 million.19
Eight counties in Central Virginia were included
in the declared disaster area; Louisa County alone
received almost 1,500 damage reports from residents.19 The entire Louisa County school system
closed down for weeks following the earthquake,
and two schools were considered damaged beyond
repair.20 Only 11 miles from the epicenter, the
North Anna Nuclear Generating Station experienced an automatic safe-shutdown—the first
safe automatic shutdown of a nuclear power plant
in U.S. history.21 Although ground motion from
the earthquake exceeded plant seismic design
levels, the station experienced only minor structural damage and no critical structures were
affected.22 The earthquake also triggered several
small rock falls, damaged two small dams, broke
a water main in the town of Mineral, and left
3,000 people without power.23 While the greatest damage occurred in Central Virginia, damage
Weldon Cooper Center for Public Service • June 2015
Figure 7: Virginia’s Network of Seismometers Provides Real-time Seismic Data
Source: The Virginia Department of Mines, Minerals, and Energy (DMME) Division of Geology and Mineral Resources (DGMR)
Note: Live seismic recordings from these stations can be viewed at the following web address:
http://dmme.virginia.gov/DGMR/PDF/Seismic_Stations.pdf
Figure 8: Generalized Felt Area with Intensities for the August 23, 2011 Earthquake
Source: The Virginia Department of Mines, Minerals, and Energy (DMME) Division of Geology and Mineral Resources (DGMR) using data
compiled from S. E. Hough, “Initial Assessment of the Intensity Distribution of the 2011 MW 5.8 Mineral, Virginia Earthquake,” Seismological
Research Letters, Vol. 83, No. 4, (2012), pp. 649-57 and the U.S. Geological Survey, “Did You Feel It?” web site: http://earthquake.usgs.gov/
earthquakes/dyfi/events/se/082311a/us/index.html
7
The Virginia News Letter
Figure 9: Property Damage from the 2011 Earthquake
“Historic epicentral
data reveals that
the majority of
Virginia’s earthquakes occur in three
zones of relatively
frequent seismicity.”
Property damage near the earthquake epicenter in Mineral, Virginia (left) and the steeple of the National Cathedral in Washington, D.C. that was displaced by the 2011 earthquake (right).
Source: Photos by Francis Ashland (left) and William Leith (right), the U.S. Geological Survey
8
was reported into Northern Virginia and Maryland. Monitoring of water wells revealed a disturbance in groundwater levels as far as 350 miles
away. 18,24 In Washington, D.C., several of the
Smithsonian Museum of Natural History’s specimen jars fell to the floor, the Washington Monument developed several cracks, and the National
Cathedral was significantly damaged.25 Enough
books fell in the University of Maryland library to
cause a temporary building shutdown.
Following the main shock, temporary seismic
networks recorded a series of over 450 aftershocks
with a magnitude greater than 1.26,21 Studying
the aftershock sequence helped to reveal the location of a previously undiscovered fault and may
suggest that there are other potentially active
faults within the area.27
Not only did the 2011 earthquake cause
structural damage, but it also left its mark in
the geologic record. Soft sediment deformation, such as sand boils (Figure 3) and sand dikes
(Figure 10) were identified within the epicentral
area following the earthquake. Although some of
these surface features were washed away by the
soon-to-follow Hurricane Irene, geologists continue to search for sub-surface deformation features that may help us learn more about the 2011
earthquake and previous seismic events in Central
Virginia.
What does Virginia’s Seismic History
Tell Us?
Historic epicentral data reveals that the majority
of Virginia’s earthquakes occur in three zones of
relatively frequent seismicity (Figure 11). Scientists have identified these “seismic zones,” along
with many other earthquake hot spots across the
eastern United States. Stretching from Richmond
to Charlottesville, the Central Virginia Seismic
Zone (CVSZ), rests largely within the Piedmont.
To the southwest, the Giles County Seismic Zone
(GCSZ) extends through the New River Valley, while the Eastern Tennessee Seismic Zone
(ETSZ) envelopes the southwestern tip of Virginia. Although it is likely that Virginia’s geologic
history has much to do with how stress from tectonic plate motion is transferred and stored within
the center of tectonic plates,28 much remains to
be discovered about why these zones exist.
By reviewing the history of earthquakes in
Virginia, we gain a better understanding for the
potential future of seismicity in our state. Historically, low magnitude earthquakes have not
been uncommon. Although less frequent, high
Weldon Cooper Center for Public Service • June 2015
Figure 10: Soft Sediment Deformation “Sand Boils”
Near the 2011 Earthquake Epicenter
understand why, where, and when earthquakes
occur. Gaining a better scientific understanding of
seismicity in the eastern U.S. will provide a stronger
foundation for local agencies and planning districts
to mitigate potential risk from future events.
Mapping Virginia Earthquake Hazards
Source: Photo by Mark Carter, the U.S. Geological Survey.
magnitude damaging earthquakes have also
occurred throughout history, and there may be evidence for these types of destructive events occurring back through thousands of years of Virginia’s
geologic past. These infrequent, but damaging
earthquakes remind us that even in the tectonically stable eastern United States seismic adjustments in the Earth’s crust are ongoing. Because
large eastern earthquakes have longer return periods, the memory of their impact is more easily lost
to history.
Prior to the careful seismic monitoring following the 2011 earthquake, the causative fault
was unknown to geologists. Thorough monitoring
and analysis of future seismic events will allow us
to build a more comprehensive earthquake history
of Virginia and help reveal the intricate network
of faults beneath our feet. With advancing science
and technology, scientists will be able to better
The 2011 Mineral earthquake was an abrupt
reminder that significant and damaging earthquakes can occur within the commonwealth.
Because earthquake prediction is not currently
possible, the continued development of regional
and local seismic hazard maps29 and the improvement of regional hazard mitigation plans will play
an important role in increasing Virginia’s future
earthquake preparedness. The 2011 earthquake
illustrates that a variety of factors should be considered when evaluating potential risk and hazard
mitigation. Not only is basic building construction
an important consideration, but other impacts to
infrastructure such as power outages and damage
to dams, pipelines, and bridges may occur. Earthquakes may also cause temporary to permanent
changes in aquifers. Rock falls and landslides can
cause additional damage.
In an effort to improve our understanding
of Virginia’s seismic zones and related hazards,
the Division of Geology and Mineral Resources
(DGMR) is participating in a project funded
through FEMA’s Hazard Mitigation Grant Program and managed by the Virginia Department
of Emergency Management (VDEM). As part of
this project, the DGMR is evaluating Virginia’s
“Prior to the careful
seismic monitoring following the
2011 earthquake,
the causative fault
was unknown to
geologists.”
Figure 11: Virginia’s Seismic Zones are Defined by Areas of Increased Earthquake Frequency
Source: The Virginia Department of Mines, Minerals, and Energy (DMME) Division of Geology and Mineral Resources (DGMR)
9
The Virginia News Letter
“In addition to
assessing Virginia’s
seismic hazards,
effective communication of earthquake
hazards and potential risk is imperative to improving
Virginia’s preparedness for future
seismic events.”
seismic history and producing a geologic fault
geodatabase, focusing on the three defined areas
of greatest seismic activity in Virginia. The geodatabase will be a compilation of faults, at varying
scales, mapped by geologists over approximately
the past 100 years. The incorporation of new
technology, like high-resolution remotely-sensed
digital elevation data (Light Detection and Ranging—LiDAR) may also help identify topographic
features and offsets that indicate the presence of
previously unrecognized faults.
Assessing the commonwealth’s seismic hazards involves defining areas of greatest risk.
Earthquakes that occur in areas of high population density, with considerable development, have
the potential to do the most damage. Overlaying
cultural data with geologic fault mapping will
help to identify communities and infrastructure
potentially at risk to future earthquake damage.
In addition to assessing Virginia’s seismic hazards, effective communication of earthquake hazards and potential risk is imperative
to improving Virginia’s preparedness for future
seismic events. The DGMR is collaborating with
emergency management and planning agencies to
increase public understanding of seismic hazards
and improve possible hazard mitigation.
Virginia is divided into 21 planning district
commissions (PDCs) (Figure 12). Each PDC
is composed of local government elected officials and appointed citizens, who “…promote the
orderly and efficient development of the physical,
social and economic elements of the district by
planning, and encouraging and assisting localities to plan, for the future.”30 Under the Disaster Mitigation Act of 2000, Virginia’s planning
district commissions develop Hazard Mitigation
Plans that attempt to identify natural hazards
with the potential to impact that location, assess
potential damage to infrastructure and the public
that could result, and present strategies that may
help mitigate such loss. The DGMR is collaborating with the twelve Virginia districts that overlap
Virginia’s seismic zones. Although each district
discusses earthquakes as a potential natural disaster within its hazard mitigation plan, the plans are
updated every five years, presenting an opportunity to incorporate new scientific information to
improve mitigation strategies.
Conclusions
Earthquakes are a significant geologic hazard in
the United States. Although much research has
focused on the active tectonic setting of the western U.S., seismicity in the eastern U.S. is not as
well understood. Over hundreds of millions of
years of geologic time, Virginia has developed a
complex underground network of geologic faults.
Motion along some of these faults has caused
hundreds of earthquakes documented throughout
Virginia’s history. Although severe earthquakes
are relatively infrequent, they have occasionally
Figure 12: Virginia Planning District Commissions and Overlapping Seismic Zones
10
Source: The Virginia Department of Mines, Minerals, and Energy (DMME) Division of Geology and Mineral Resources (DGMR)
Weldon Cooper Center for Public Service • June 2015
shocked Virginia residents with their destructive
power. The 2011 event in central Virginia was a
reminder of that potential.
As Virginia’s population and infrastructure
continue to grow, so too will seismic-related risk.
Studying Virginia’s seismic history and real-time
monitoring of modern earthquakes by permanent
eastern seismic networks will help scientists better understand regional seismicity. Tools such as
a comprehensive geologic fault database will be
helpful in assessing seismic hazards and identifying areas of greatest risk. Such information will
enable planning district commissions to continuously improve their Hazard Mitigation Plans and
increase preparedness for future seismicity in the
commonwealth.
Useful Resources
Readers who want to learn more about earthquakes can go to many sources on the web. Table
2 lists several.
ABOUT THE AUTHORS:
Wendy Kelly is a geologist working for the Virginia Division of Geology and Mineral Resources
in Charlottesville. She completed a M.S. in geology at Oregon State University and an undergraduate degree in geology from Hampshire
College in Massachusetts. She has worked at the
U.S. Geological Survey in Florida, the Vermont
Geological Survey, and with the National Park
Service. Wendy is particularly interested in how
science is communicated to the public.
Anne Witt is a geologist with the Virginia
Division of Geology and Mineral Resources in
Charlottesville. She has been working in geologic hazards for over 12 years and specializes in
using geographic information systems (GIS) to
map and model natural hazards. She has a M.S.
in geology from North Carolina State University
and a B.S. in geology from the University of Mary
Washington.
Table 2: Web Links for Useful Information About Earthquakes
Topic
Web Link
What to do in the event of an earthquake
www.shakeout.org
Learn more about earthquakes in Virginia
http://dmme.virginia.gov/DGMR/earthquakes.shtml
Learn more about active seismometers in
Virginia
http://www.magma.geos.vt.edu/vtso/
U.S. Geological Survey hazard maps
http://earthquake.usgs.gov/hazards/
Add your own earthquake observations to a
national earthquake database
http://earthquake.usgs.gov/earthquakes/dyfi
Become better informed about Virginia’s
planning districts
http://www.vapdc.org/
Learn more about how earthquakes are
measured
http://www.usgs.gov/faq/taxonomy/term/9828
Endnotes
1 M. Gall, K.A. Borden, C.T. Emrich, and S.L. Cutter, “The
Unsustainable Trend of Natural Hazard Losses in the United States,”
Sustainability 3 (2011), pp. 2,157-81.
2 A. McGarr, D. Simpson, and L. Seeber, “40 Case Histories of
Induced and Triggered Seismicity,” International Geophysics, Vol. 81A,
(2002), pp.647-661.
3 U.S. Geological Survey http://earthquake.usgs.gov/research/
induced/
4 D.P. Schwartz, W.B. Joyner, R.S. Stein, R.D. Brown, A.F. McGarr,
S.H. Hickman, and W.H. Bakun, “Review of Seismic Hazard Issues
Associated with the Auburn Dam Project, Sierra Nevada Foothills,
California,” U.S. Geological Survey Open File Report 96-0011 (1996).
5 Ebasco Services Incorporated, “Studies of Speleothem Deposits in
the Giles County, VA Seismic Zone,” Progress Report for April and
May (1993).
6 S.F. Obermeier and W.E. McNulty, “Paleoliquefaction Evidence
for Seismic Quiescence in Central Virginia during Late and Middle
Holocene Time,” EOS, Transaction of the American Geophysical
Union, Vol. 79, No. 17, Spring Meeting Supplement, Abstract
T41A-9, (1998).
7 W.C. Burton, R.W. Harrison, D.B. Spears, N.H. Evans, and S.
Mahan, “Geologic Framework and Evidence for Neotectonism in
the Epicentral Area of the 2011 Mineral, Virginia, Earthquake,” The
Geological Society of America Special Paper 509, (2015).
8 J.A. Bear, Jr. and L.C. Stanton, eds. Jefferson’s Memorandum
Books: Accounts, with Legal Records and Miscellany, 1767-1826.
(Princeton, NJ: Princeton University Press, 1997).
9 M.G. Hopper, and G.A. Bollinger, “The Earthquake History of
Virginia, 1774 to 1900,” Virginia Polytechnic Institute and State
University, Blacksburg, Va., (1971).
10 The Virginia Gazette, February 24, 1774, p. 3.
11 G.R. MacCarthy, “An Annotated List of North Carolina
Earthquakes,” Journal of the Elisha Mitchell Scientific Society, Vol. 73,
(1957), pp. 84-100.
12 C.W. Stover and J.L. Coffman, “Seismicity of the United States,
1568-1989 (Revised),” U.S. Geological Survey Professional Paper
1527, (1993) pp. 375-78.
13 G.R.MacCarthy, “A Descriptive List of Virginia Earthquakes
through 1960,” Journal of the Elisha Mitchell Scientific Society, Vol. 80,
No.2 (1964), pp. 95-114.
11
The Virginia News Letter
14 G.A. Bollinger, and C.W. Stover, “List of Intensities, Epicentral
Distances, and Azimuths for the 1897 Giles County, Virginia,
Earthquake and the 1969 Elgood, West Virginia, Earthquake,” USGS
Open-File Report 78-1017, (1978).
15 J.L. Coffman and C.A. von Hake, “Earthquake History of the
United States,” U.S. Department of Commerce, NOAA and U.S.
Department of the Interior, Geological Survey, Publication 41-1,
(1982).
16 M.R. Campbell, “Earthquake Shocks in Giles Co., Va,” Science,
Vol. 7, No. 164, p. 233-235, (1898).
17 N. H. Heck, “Earthquake History of the United States,”
Department of Commerce U.S. Coast and Geodetic Survey Special
Publication No. 149 (1928).
18 J.W. Horton and R.A. Williams, “The 2011 Virginia Earthquake:
What are Scientists Learning?,” EOS, Vol. 93, No. 33, p. 317-318,
(2012).
19 GEER (Geotechnical Extreme Events Reconnaissance)
Association. Geotechnical quick report on the affected region of the
23 August 2011 M5.8 Central Virginia earthquake near Mineral,
Virginia, GEER Association Report No. GEER-026 (2011).
20 M.J. Heller and A.M. Carter, “Residential Property Damage
in the Epicentral Area of the Mineral, Virginia, Earthquake of 23
August 2011,” The Geological Society of America Special Paper 509,
(2015).
21 D. F. Fenster and L. S. Walsh, “Preliminary information on the
Mw 5.8 Mineral, VA, earthquake,” AEG News, Vol. 54, No.4, p. 26–30,
(2011).
22 Y. Li, G.L. Stirewalt, and K.A. Monoly, “Overview of
Performance of the North Anna Nuclear Power Station during
the 2011 Mineral, Virginia, Earthquake and Continued Seismic
Evaluations,” The Geological Society of America Special Paper 509,
(2015).
23 R.A Green, S. Lasley, M.W. Carter, J.W. Munsey, B.W. Maurer,
and M.P. Tuttle, “Geotechnical Aspects in the Epicentral Region of
the 2011 Mw 5.8 Mineral, Virginia, Earthquake,” The Geological
Society of America Special Paper 509, (2015).
24 E.A Roeloffs, D.L. Nelms, and R.A. Sheets, “Widespread
Groundwater-Level Offsets Caused by the Mw 5.8 Mineral, Virginia,
Earthquake of 23 August 2011,” The Geological Society of America
Special Paper 509, (2015).
25 D. Wells, J.A.Egan, D.G Murphy, and T. Paret, “Ground Shaking
and Structural Response of the Washington Monument During the
2011 Mineral, Virginia, Earthquake,” The Geological Society of
America Special Paper 509, (2015).
26 A.W. Horton Jr., M.C. Chapman, and R.A. Green, “The 2011
Mineral, Virginia, Earthquake, and its Significance for Seismic
Hazards in Eastern North America - an Overview,” The Geological
Society of America Special Paper 509, (2015).
27 A.W. Horton Jr., A.K. Shah, D.E. McNamara, S.L. Snyder, and
A.M. Carter, “Aftershocks Illuminate the 2011 Mineral, Virginia,
Earthquake Causative Fault Zone and Nearby Active Faults,” The
Geological Society of America Special Paper 509, (2015).
28 A. Gangopadhyay and P. Talwani, “Symptomatic Features of
Intraplate Earthquakes,” Seismological Research Letters, Vol. 74, No. 6,
(2003).
29 For example: M.D. Petersen, M.P. Moschetti, P.M. Powers, ,
C.S. Mueller, K.M. Haller, A.D. Frankel, Y. Zeng, S. Rezaeian, S.C.
Harmsen, O.S. Boyd, N. Field, R. Chen, K.S. Rukstales, N. Luco, R.L.
Wheeler, R.A. Williams, and A.H. Olsen, “Documentation for the
2014 Update of the United States National Seismic Hazard Maps,”
U.S. Geological Survey Open-File Report 2014–1091, ( July 17, 2014)
http://dx.doi.org/10.3133/ofr20141091.
30 Virginia General Assembly Legislative Information System, Code
of Virginia 15.2-4207
(https://leg1.state.va.us/cgi-bin/legp504.exe?000+cod+15.2-4207)
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Editor: John L. Knapp
VOL. 91 NO. 2 JUNE 2015
Consulting Editor: Robert Brickhouse
The Virginia News Letter (ISSN 0042-0271) is published by the Weldon Cooper Center for Public Service, University of Virginia,
P.O. Box 400206, Charlottesville, Virginia 22904-4206; (434) 982-5704, TDD: (434) 982-HEAR.
Copyright ©2015 by the Rector and Visitors of the University of Virginia. The views expressed are those of the author and not the official position
of the Cooper Center or the University.
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