1) What is the goal of
the research SMU is conducting into the recent spate of small
earthquakes in the Reno-Azle area?
The primary research goal
for the SMU seismology team will be to collect data from multiple
locations and analyze that data to improve our understanding of the
earthquake locations, size, fault plane solutions (geometry of the fault
movement) and accelerations associated with the events. We do not know
if we will collect enough data to point to a cause of the earthquakes.
2) How is SMU conducting the
Reno-Azle area research?
SMU has deployed several
different types of earthquake monitors in the region: We first deployed
five NetQuakes stations provided by the Unites States Geological Survey
in the area identified as the epicenter for the quakes that occurred
through January 2014. These small instruments are designed to be
installed in private homes, businesses, public buildings and schools.
The raw, waveform data
recorded by the Netquakes monitors is streamed to SMU over wireless and
cell modem networks, where we identify and relocate earthquakes that are
too small (~M<2.2) for the USGS to pick up at the National Earthquake
Information Center. The USGS Data from the last 30 days of monitoring in
the Reno-Azle area is available online through the USGS at
Other monitors are being deployed throughout the region.
We have deployed seven continuous recording, higher performance
seismic sensors to date. See how SMU teams installed one of
these monitors by clicking here.
3) How long will the
Reno-Azle study take to complete?
We will continue to
monitor the earthquake sequence over the next six months to a year,
unless activity remains high. We have not determined a timeline for
completing additional studies. We do not consider our seismic studies
complete until results have been published in peer-reviewed literature,
which is the traditional, academic process that provides for thorough
review of research methods and conclusions by qualified peers from
within that scientific discipline. Past studies of seismicity in the
Dallas-Fort Worth area have taken one to two years.
4) Can the Reno-Azle
research determine if the earthquakes in that area are connected to
wastewater injection wells operating nearby?
Understanding if and/or
how wastewater injection wells contribute to seismicity requires not
only improved identification of earthquake locations, but also
high-resolution well log data and subsurface information about rock
type, permeability, porosity and fault structures. Much of this data is
collected by oil and gas companies as part of exploration and
pre-drilling site verification, and ultimately it will take the
cooperation and data sharing between the private and public sectors to
make progress on this important science topic. We cannot say at this
time if we will be able to definitively, and in a scientifically
verifiable way, show if the Reno-Azle sequence are induced or natural
5) Can the Reno-Azle
research determine why North Texas as a whole is seeing in increase in
felt seismicity in recent years?
No, an individual study
of one active earthquake sequence, such as the Reno-Azle sequence, will
not be able to address the larger question of increased seismicity
throughout North Texas. Long-term regional seismic monitoring would be
helpful in order to assess the true background seismicity rate in the
region and better capture small magnitude (M<3) earthquakes.
6) Who is SMU conducting
its research for?
We hope to provide the
residents of the Reno-Azle area with more accurate information regarding
the ongoing earthquake sequence. Financial support has been provided
through Southern Methodist University with significant instrumentation
and analysis support provided by the U.S. Geological Survey.
7) The residents in the
Reno-Azle area have a lot of questions about these quakes. Is there
anything SMU seismologists can do to help them understand what’s going
This SMU website provides
links to the U.S. Geological Survey Earthquake Education webpage and the
Texas Earthquakes webpage supported by the University of Texas at
Austin. SMU seismologists also provide data to the Texas Railroad
Commission and local municipalities upon request. Additionally, we have
purchased an Incorporated Research Institutions for Seismology (IRIS)
Active Earth Monitor, which is a customizable computer-based earth
science display designed for schools, libraries, etc. The system
provides an interactive way to learn about earthquakes. We are designing
a Reno-Azle-specific module for this system and plan to place the system
in a public area in the Reno-Azle area as soon it is delivered in March
or April 2014.
9) People don’t think of
Texas as an earthquake-prone region. Should we assume that the recent
spate of earthquakes are induced by human activity, like injection
observations in Texas recorded by monitoring equipment are limited to
only the last few decades, with the best records generated in only the
last 20 years. This is a relatively short period for earthquake
observations. While we typically can extend the observations with
historical records, these record only the reports of earthquakes people
could actually feel – a historically sparse record. Texas does have a
history of small naturally occurring earthquakes associated with the
many existing faults in the subsurface. Further information about
earthquakes throughout Texas can be found at
There are ~30,000
wastewater injection wells in the US, and the vast majority of them are
located in areas where there have been no detected earthquakes. In 2011,
there were eight case studies linking earthquakes to these wastewater wells in the US
al, 2012 National Research Council,
http://www.nap.edu/catalog.php?record_id=13355). The question is
why? Understanding why a particular injection case might be associated
with earthquakes while another similar well injecting under similar
conditions seems not to be seismic is a critical question.
Finding the answers is
complicated by the relationship of geology (such as the location of
faults) to oil and gas production (extraction) or to wastewater disposal
(injection), and even our growing ability to sense and locate
earthquakes. It will take collaboration and shared data between
scientists, industry and government to provide better information on the
causes of induced seismicity.
10) Two previous SMU
studies have investigated connections between wastewater injection wells
and seismicity – in the area around DFW Airport in 2009 and in the
Cleburne area in 2010. Does that mean that wastewater iniection wells
caused those earthquakes?
Both studies examined the
temporal and spatial relationship between nearby injection wells and the
earthquake sequences. For the DFW airport study, the fact that the
injection well began operating shortly before the earthquakes began and
that the earthquakes were close to the well, provided a plausible
indication that injection was in some way related to the start of
earthquakes. In the case of the Cleburne area, although injection wells
were located within a few kilometers of the earthquakes, there was not
the strong timing relationship. However, because there were no reported
earthquakes prior to injection, the paper was not able to reject
injection as a possible cause. This is a weaker conclusion than in the
Both studies suffered
from a lack of a physical explanation (a model) for exactly how fluid
injection at specific sites could have resulted in the earthquake
evolution over the observation period. Neither study contained a
detailed understanding of the fault geometry, subsurface geology, and
subsurface stress regimes. Neither study investigated similar natural
sequences or similar injection histories with no associated
earthquakes. Without this understanding, neither study was able to
suggest the future probability of larger events needed to develop the
hazard associated with this fault. Without such understanding,
seismologists are limited to using relatively crude statistical methods
based on the observation history in similar tectonic regions in the U.S.
11) Is it accurate to
describe the earthquakes that have been occurring in North Texas as
No. Hydraulic fracturing
or “fracking” is the process of creating fractures in subsurface rock
formations by injecting fluid into cracks to create larger underground
fissures, allowing more oil and gas to flow out of rock formations, from
where it can be extracted. The largest resulting seismic activity from
hydraulic fracturing is typically hundreds to thousands of times smaller
than the smallest earthquake that human beings can feel. In examining
all reports worldwide, there have been only a few instances where
hydraulic fracturing did appear to directly trigger a felt earthquake
out of tens of thousands of successful operations. Such instances are
very, very rare and have not, to our knowledge, happened in the North
Texas area. In the roughly 35,000 shale gas wells in the U.S., only two
case studies are known (Shemeta et al, 2012 National Research Council).
The other documented hydraulic fracturing events include the M3.5 in
Horn River, Canada, a M2.3 in Blackpool, UK in 2011, and the event in
Basel, Switzerland in 2006.
Sometimes the waste
fluids from producing oil and gas wells (those that use fracking to
reach “tight gas”, as well as those that don’t) are disposed of by
injection wells drilled below any fresh water aquifer. The wastewater
disposal is a separate process from the fracking operation itself and
may occur away from the fracked well. Injection of wastewater can occur
in oil fields unrelated to fracking.
12) What is the relationship between induced seismicity and
Induced seismicity has been related to geothermal energy
production, conventional oil and gas development (including
enhanced oil recovery [EOR]), shale gas development, injection
wells related to disposal of wastewater associated with energy
extraction, and carbon capture and sequestration. A recent
review can be found in Shemate et al, National Research Council,
13) Where can I find additional information on induced
seismicity in the United States?
The United States Geological Survey webpage on Induced
Seismicity contains information, videos and links that address