Description of the Research Opportunity
The earthquake rate in the central United States increased more than tenfold in the 15 years since 2009. 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 like wastewater disposal and hydraulic fracturing. Multiple magnitude 5+ earthquakes have occurred during this surge in seismicity in Oklahoma and Texas, including the 2016 M5.8 Pawnee earthquake, the M5.0 Cushing earthquake that occurred near the largest oil storage facility in the country, the 2022 M5.2 Range Hill earthquake that occurred 20 km from Midland, Texas, and three M5+ earthquakes that occurred within 10 km of each other in the Coalson Draw, Texas region between 2020 and 2023.
While the dramatic increase in injection-induced seismicity is primarily caused by oil and gas related wastewater disposal, geothermal energy production has long contended with induced seismicity concerns dating back to early development in Basel, Switzerland, in 2006 and Pohang, South Korea, in 2017. Geologic carbon sequestration (GCS) has, so far, not produced significant magnitude seismicity largely owing to the sparsity of commercial scale projects. However, the similarities of the physical settings between GCS and oil and gas wastewater disposal suggest that induced seismicity might become a hazard with wide-spread adoption of GCS.
Numerous studies of injection-induced earthquakes have been carried out over the past 15 years, but there are still an extraordinary number of unanswered questions. Of particular interest is understanding what the operational and geological controls are on whether earthquakes are likely to be induced by injection activities of any kind.
We seek a Mendenhall Postdoctoral Scholar to investigate induced seismicity through detailed analyses of geophysical data in regions of active injection (oil and gas, geothermal, and/or carbon sequestration) with the broad goal of understanding the physical processes underpinning and controlling injection-induced seismicity.
The candidate could explore a wide range of topics, including but not limited to:
- Seismology:
- Spatiotemporal analysis: Induced earthquake sequences can reveal details about preexisting fault structures and the evolution of stresses due to changes fluid pressures and poroelastic stresses.
- Source properties: Induced earthquakes are responding to rapid changes in stress and are often occurring on faults that have not slipped in hundreds of years or more. Given that these conditions are different than for most natural earthquakes, analysis of source properties may reveal variations in the source physics of induced earthquakes.
- Temporal evolution of subsurface properties: Subsurface injection of fluids undoubtedly changes the conditions at depth both through increased fluid pressures and the poroelastic response of the host rock. Changes in these properties would 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.
- Forecasting:
- Physics-based forecasts: Recent work has shown physics-based forecasting of induced seismicity hazard, where seismicity rates are simulated from injection rates, may be more accurate than purely statistical approaches. However, there are outstanding questions regarding appropriate modeling choices and methodologies that warrant further study.
- Statistics-based forecasts: Probabilistic seismic hazard forecasts rely on statistical seismicity rate models to forecast future earthquake occurrence rates. There are many open questions about how best to model the space-time evolution of induced seismicity for USGS seismic hazard products, from short timescales of days (e.g., applying Operational Aftershock Forecasting methods such as the Epidemic Type Aftershock Sequences (ETAS) model) to long timescales of decades (e.g., treatment of induced seismicity in the long-term National Seismic Hazard Model).
- Numerical modeling: Numerical modeling of the seismic response to injection can yield valuable insights into determining which operational and geologic parameters influence whether injection wells are likely to induce earthquakes; the physics underpinning induced and natural seismicity; and providing enhanced input into the National Seismic Hazard Model for induced seismicity.
- Geodesy: Subsurface injection and extraction of fluids has been seen to cause measurable ground deformation. Observation of this deformation, or the lack thereof, gives clues into how the subsurface is responding to the changes in fluid in the system, and how moment is released in the form of seismic waves and/or slow (aseismic) slip. Developing methods to forecast and later test for ground deformation due to injection would be valuable in understanding induced seismicity and particularly useful in calibrating hazard forecasts. Geodetic data can also be used to image the rupture of induced earthquakes, which may reveal a connection between their rupture behavior and injection operational patterns.
- Geomechanics: Induced seismicity is fundamentally a geomechanical problem. A deeper understanding of the state of stress and how materials at depth are responding to the changes in stress conditions caused by injection can be used to inform larger scale models of induced seismicity. With additional instrumentation for in-situ measurements of strain and pore pressure coming online, there are many opportunities to carefully characterize this behavior. Geomechanics can also be used to forecast reservoir integrity in response to strong shaking – a key issue for carbon sequestration and geothermal systems.
Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.
Proposed Duty Station(s)
Moffett Field, California
Pasadena, California
Golden, Colorado
Areas of PhD
Geophysics, seismology, geodesy, geomechanics, or related fields (candidates holding a Ph.D. in other disciplines but with knowledge and skills relevant to the Research Opportunity may be considered).
Qualifications
Applicants must meet one of the following qualifications: Research Geophysicist, Research Geologist, Research Civil Engineer, or Research Petroleum Engineer.
(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.)
