University of Southern California Global Energy Network The USC Andrew and Erna Viterbi School of Engineering USC

 Frequently Asked Questions (Click to download)

 
1. What is the Induced Seismicity Consortium?
The Induced Seismicity Consortium (ISC) is a collaborative effort of scientists from the
University of Southern California (USC) based Southern California Earthquake Center
(SCEC). The SCEC includes representatives from the USC Department of Civil and
Environmental Engineering, USC Petroleum Engineering program, as well as
representatives from industry, national laboratories, regulatory agencies, non-
governmental organizations, and community groups interested in developint science-
based understanding of the causes and risks of induced seismicity.
 
2. What is induced seismicity?
 
Induced seismicity is seismic activity that occurs as a result of human activity
(anthropogenic). Seismic activity refers to the frequency, type and size of earthquakes.
The vast majority of earthquakes are natural, caused by stresses that cause fracturing of
rock in the earth’s crust. Examples of processes that might cause induced seismicity
include subsurface wastewater injection, geothermal energy generation, and surface-
water reservoir impoundment. Most seismic events related to induced seismicity cannot
be felt by humans, because they have very low magnitudes (less than 2 on the Richter
scale) that can only detected by specialized instruments.
 
3. What causes induced seismicity?
 
The main cause of induced seismicity is increased fluid pressure in rock pores that
reduces that natural friction and allows slippage of rocks along a fault1.  Researchers
investigating causes of induced seismicity have documeted that fluid pressures have a
role in seismicity2.  As explained by the U.S. Department of Energy (DOE), “pore
pressures act against the weight of rock and forces holding the rock together; if the pore
pressures are low, then only the imbalance of natural in situ earth stresses will cause an
occasional earthquake. If, however, pore pressures increase, then it would take less of
an imbalance to cause an earthquake3.” 
Cases have recently been observed in Oklahoma and Ohio, were seismic activity has
been associated with the disposal of large volumes of wastewater into deep geologic
formations4.  Such injection can disrupt the balance of stress within rock, especially
when not paired with corresponding fluid withdrawl. Other potential sources of induced
seismicity include underground mining, and chemical interaction of fluids with rock
materials5
 
4. Can hydraulic fracturing cause induced seismicity?
Hydraulic fracturing is a well stimulation practice that uses the injection of fluid to open
flow channels in tight formations to produce the hydrocarbons locked within them6 . The
practice has been in use for over sixty years.
A report published in 2013 by the National Academies of Science concluded that
hydraulic fracturing does not pose a high risk for inducing seismic events that could be
felt by humans. The U.S. Geological Survey (USGS) has also found that hydraulic
fracturing is not a substantial cause of induced seismicity, and that “only very rarely” is
hydraulic fracturing the cause of any earthquakes that can be felt by humans. The
“microearthquakes” that hydraulic fracturing creates are too small to be felt or cause
structural damage7.  Hydraulic fracturing has been associated with only minor sesmic
events at two U.S. locations, neither in California.
Accordingly the U.S. Department of Energy has also concluded that hydraulic fracturing
is “rarely, if ever, a hazard when used to enhance permeability in oil and gas or other
types of fluid-extraction activities8.”  Furthermore, the USGS finds that “although the
disposal process has the potential to trigger earthquakes...very few of the more than
30,000 wells designed for this purpose appear to cause earthquakes9.” 
 
5. How can one determine whether a seismic event is natural or induced?
In their 1993 paper10 , Davis and Frohlich set forth a simple set of yes or no questions
that could be used as a rubric in determining whether a seismic event was likely
induced. The questions were as follows:
 
1. Are these events the first known earthquakes of this character in the region?
2. Is there a clear correlation between injection and seismicity?
3. Are the epicenters near wells (within five kilometers)?
4. Do some earthquakes occur at or near injection depths?
5. If not, are there known geologic structures that may channel flow to sites of earthquakes?
6. Are changes in fluid pressure at well bottoms sufficient to encourage seismicity?
7. Are changes in fluid pressure at hypocentral locations sufficient to encourage
seismicity?
From these, an even may be scored, with more “yes” answers indicating an increased
likelihood of an event having been induced.

6. Has hydraulic fracturing caused earthquakes in California?
A recent study by the USC Induced Seismicity Consortium (ISC) found no correlation
between hydraulic fracturing and induced seismic activity in California11 . This study
evaluated 30 years of seismic data in areas of oil production where hydraulic fracturing
has been used in California and found little or no correlation between oil field activities
in general and seismic activity.
 
The ISC study compared seismic activity from 1980 to 2013 with oil field activity,
including hydraulic fracturing, at locations throughout California. Oil field activities and
well locations were obtained from the California Division of Oil, Gas, and Geothermal
Resources (DOGGR) and the FracFocus website. Seismic activity data were compiled
from the Northern and Southern California Earthquake Centers, and included epicenter
locations of seismic activity and the magnitudes and depths of seismic events. Database
maps were prepared to display oil and gas well locations, well type (e.g. oil or gas
producer, water flood injector, steam flood injector, water disposal), type of activity
(drilling, producing, injecting, completing, stimulating, or abandoning), and the depth of
the activity.
 
Composite maps were prepared comparing locations of seismic events and known
geologic faults with oil and gas well locations and oil field activities. Statistical analyses
were conducted to determine whether there was any correlation between seismic
events and oil field activities. Little or no correlation was found. For example, in
northern California, a total of 303,609 seismic events recorded from 1980-2013. The
main area of northern California where oil and gas activities have occurred is in the
Sacramento area, far from known fault zones, where oil is produced from shallow
depths (less than 6 kilometers). Of the total 303,609 seismic events in northern
California, only 210 event were in the Sacramento area, only 3 seismic events had
magnitudes greater than 3, and none was greater than 4.
 
7. Does induced seismicity from wastewater injection by the oil industry differ in
California than in other states?
 
The practice of deep wastewater injection is commonly used in states throughout the
U.S. and is strictly regulated by state and federal laws. California has strict regulations
governing subsurface wastewater injection. Injection wells used by the oil industry in
California are different from the injection disposal wells linked to earthquakes in other
states, like Ohio Oklahoma, Texas, and Arkansas12. In California oil fields, wastewater is
reinjected back into the formation after the oil is removed13.  In California, the water is
injected into porous sandstone reservoirs, from which water and oil was originally
removed. In other areas of the U.S., wastewater is often injected into rocks with little
porosity and storage capacity. Pore pressures in the rock increases dramatically as the
limited available pore space is filled and, additional injected water causes the rock to
break, causing an induced seismic event. As a result, a University of California Santa
Barbara geophysicist, Craig Nicholson, concluded that “very little of the state’s
[California] earthquake activity can be tied in any way to reinjection...there’s not a
connection like there is in the central and eastern United States.”
 
8. How do we know if an earthquake was caused by induced seismicity?
 
Seismologists conduct extensive analysis of earthquake data and potential
anthropogenic factors to determine whether an earthquake is natural, triggered or
induced. More information is needed to improve researchers’ understanding of the
“triggering” mechanisms of injection and production-related induced seismicity as well
as any irregularities that naturally occurring earthquakes may have14
Recent studies by USC and the California Institute of Technology indicate that there is
not a significant correlation between earthquakes and oil and gas field operations. A
major reason for this is that natural earthquake epicenters are typically at depths below
five kilometers, while oil field operations are conducted at depths shallower than two
kilometers, typically less than one kilometer.
 
9. Are there any documented cases of injuries or property damage caused by induced
seismicity?
 
There have been no documented cases in California where injuries or property damage
been have caused by induced seismicity. However, property damage has been
documented from shaking thought to be a result of wastewater injection into rock
formations adjacent to known faults.
According to the National Research Council’s Committee on the Induced Seismicity
Potential in Energy Technologies Report15 , virtually all induced seismicity attributed to
energy development has been small in magnitude, and unable to be felt. The same
committee also concluded that hydraulic fracturing does not pose a high risk triggering
noticeable seismic activity.
 
10. What are the relevant federal, state, non-governmental organizations, and trade
associations that have information about induced seismicity and how can they be
contacted?
NATIONAL
United States Geological Survey
Arthur McGarr, Researcher, Media Relations for Induced Seismicity
650.329.5645
mcgarr@usgs.gov
Web Information: energy.usgs.gov

National Research Council
Induced Seismicity ad hoc Study Committee
http://www.nap.edu/catalog.php?record_id=13355Elizabeth Eide, Study Director
E-mail: EEide@nas.edu
 
Interstate Oil and Gas Compact Commission (IOGCC)
Mike Smith, Executive Director
P.O. Box 53127
Oklahoma City, OK 73152
(405) 525-3556
Mike Smith
mike@iogcc.state.ok.us

National Energy Technology Laboratory
Grant Bromhal, Rock Fluid Geophysics Team Lead
304.285.4688
grant.bromhal@netl.doe.gov
Web Information: http://esd.lbl.gov/research/projects/induced_seismicity/
 
 
For media interview requests or to contact the consortium researchers please contact:
Megan Hazle
Media Relations Specialist, USC Viterbi School of Engineering
hazle@usc.edu
213-821-1887

NOTES

1 http://www.gwpc.org/sites/default/files/events/white%20paper%20-%20final_0.pdf
2 U.S. Department of Energy, ‘Induced Seismicity Primer’: http://esd.lbl.gov/research/projects/induced_seismicity/primer.html
3 U.S. Department of Energy, ‘Induced Seismicity Primer’: http://esd.lbl.gov/research/projects/induced_seismicity/primer.html
4 Ozarks Public Radio, ‘USGS: Oka Fracking Has Increased Chance of ‘Damage Quake’’: http://ksmu.org/npr/usgs-okla-fracking-has-increased-chance-damaging-quake
5 U.S. Department of Energy, ‘Induced Seismicity Primer’: http://esd.lbl.gov/research/projects/induced_seismicity/primer.html
6 U.S. Department of Energy, ‘Induced Seismicity Primer’: http://esd.lbl.gov/research/projects/induced_seismicity/primer.html
7 USGS ‘Man-Made Earthquakes Update’ http://www.usgs.gov/blogs/features/usgs_top_story/man-made-earthquakes/
8 U.S. Department of Energy, ‘Induced Seismicity Primer’: http://esd.lbl.gov/research/projects/induced_seismicity/primer.html
9 USGS ‘Man-Made Earthquakes Update’ http://www.usgs.gov/blogs/features/usgs_top_story/man-made-earthquakes/
10 Davis, S.D. and C. Frohlich, 1993, did (or will) Fluid Injections Cause Earthquakes? – Criteria for a
Rational Assessment, Seismological Research Letters, 64(3-4), p. 207-224.
11 “Application of Induced Seismicity Mapping (ISM) Software - in Wilmington Oil Field,” Chen et. al.
12 Energy in Depth California, ‘Earthworks Study Makes Shaky Assumptions on California
Earthquakes,”http://energyindepth.org/california/earthworks-study-shaky-assumptions-california-earthquakes/
13 Energy in Depth California, ‘Earthworks Study Makes Shaky Assumptions on California Earthquakes,”http://energyindepth.org/california/earthworks-study-shaky-assumptions-california-
earthquakes/
14 U.S. Department of Energy, ‘Induced Seismicity Primer’: http://esd.lbl.gov/research/projects/induced_seismicity/primer.html
15 http://www.nap.edu/catalog.php?record_id=13355