The earthquake rate in the central United States has increased more than tenfold since 2008. The rate change is not a natural phenomenon but can, instead, be explained as a dramatic increase in the number of earthquakes induced by fluid-injection activities. Multiple magnitude 5+ earthquakes have occurred during this surge in seismicity including the M5.8 Pawnee earthquake and the M5.0 Cushing earthquake that occurred near the largest oil storage facility in the country.
Numerous studies of injection induced earthquakes have been carried out over the past 10 years, but there are still an extraordinary number of unanswered questions. Of particular interest is understanding what the operational and geological controls are in determining whether earthquakes will or will not be induced by injection activities.
We seek a Mendenhall Postdoctoral Scholar to investigate induced seismicity through detailed analyses of seismic data in regions of active injection with the broad goal of understanding and mitigating the hazard due to injection-induced seismicity. While the candidate is free to use existing data sets or collect new data, we encourage proposals to focus on high-quality data sets that the USGS has already collected including: a seismic deployment in southern Kansas from 2014-2019, a nodal seismic deployment in northern Oklahoma, and an upcoming seismic deployment in the Permian Basin.
The candidate could explore a wide range of topics, including but not limited to:
- Spatiotemporal evolution and statistical analysis: The spatiotemporal evolution of induced sequences in relation to injection parameters (e.g. pressure, volume, rate) is highly variable. In some cases, sequences have been shown to migrate away from injection wells, as expected from pore pressure front propagation, but in other instances the seismicity jumps around, sometimes even migrating towards injection wells. Some seismic sequences are dominated by foreshock-mainshock-aftershock interactions, while others appear more swarm-like. It is not clear what conditions control these behaviors.
- Source properties: Careful computation of earthquake source properties may reveal information on the earthquake physics and conditions at depth. Additionally, comparing source properties for induced events to those of tectonic events may provide a way to discriminate between induced and natural seismicity. Source analysis may also reveal whether stress drops vary through time.
- Temporal evolution of earth properties: Subsurface injection of fluids undoubtedly changes the conditions at depth both through increased fluid pressures and the poro-elastic response of the host rock. If these changes are large enough, they may be observable through seismological techniques. Seismological observables that may be influenced by the injection of fluids include: seismic velocities, attenuation, and anisotropy. Should we observe spatial or temporal changes in these properties, this will provide clues into where and when fluids are moving, material properties of the host rock, preferential flow directions, and could possibly give insight into the absolute stress conditions at depth.
- Numerical modeling of the seismic response to injection: Numerical modeling of the seismic response to injection can yield valuable insight into a number of areas of USGS research including: determining which operational and geologic parameters influence whether injection wells will or will not induce earthquakes; the physics underpinning induced and natural seismicity; and providing enhanced input into the national seismic hazard model for induced seismicity.
Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.
Proposed Duty Station: Moffett Field, CA
Areas of PhD: Geophysics, seismology, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).
Qualifications: Applicants must meet the qualifications for: Research Geophysicist
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)
Human Resources Office Contact: Audrey Tsujita, 916-278-9395, atsujita@usgs.gov
