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Government and public acceptance of geological sequestration of CO2 is vital for the eventual success of carbon capture and storage (CCS) initiatives. A number of factors need to be addressed to ease public apprehension. One major concern is the potential loss of caprock integrity due to earthquakes or injection-induced ground motion. This worry exists even in areas of relatively low seismic hazard.
A well-used methodology for determining earthquake hazards and ground motion is Probabilistic Seismic Hazard Assessment (PSHA). Currently, PSHA is designed for engineered structures on the surface rather than in the underground. Dr. Eaton’s team plans to customize this methodology for CCS use deep underground. Federal and provincial agencies are collaborating with the team to develop these earthquake risk assessment tools specifically for long-term geological storage of CO2. These tools will incorporate depth of burial, subsurface conditions and hazard levels appropriate to a geological storage facility designed to last for 100s of years. The approach is to examine the long-term risks, on the timescales of decades and centuries, for large earthquakes outside of Alberta. The consequences, in terms of ground motion in Alberta, will be determined with this information. Recent analog earthquake information, modern ground acceleration data, site response methods, and various models coupled with experimental validation will be used to complete the PSHA.
$72,220/ 2 years; Awarded in 2010
To become a leader and expand commercial scale CCS technology, Canada must have a complete understanding of earthquake hazard risks. This PSHA project builds on the current existing body of knowledge in Canada, and will potentially provide a robust regulatory framework for earthquake hazard analysis. It will also be critical for public acceptance for long-term CCS.
Government regulatory agencies could use this tool for earthquake risk assessment and monitoring for long-term CCS sites. Where low levels of hazard to caprock integrity can be demonstrated with the PSHA, this will help alleviate public concern. Ideally, the developed PSHA methodology will be adopted for public policy.
Dr. Eaton is partnered with the Geological Survey of Canada (specifically, Earthquakes Canada). The team is also working with the Alberta Geological Survey, which provided and analyzed data, and with the US Geological Society to train the team on stochastic modeling software.
The key goal is to adapt state of the art methodologies for earthquake hazard analysis, to better understand and/or predict the long-term risks of geological storage of CO2. The specific goals include examining regional seismicity characteristics in Alberta, creating a seismicity catalogue, computing ground motion modeling, conducting geomechanical analyses, and collaborating with public policy agencies to target functional storage life parameters.
The team has defined multiple analog earthquakes from locations which include: Tohoku, Japan; Nahanni, NWT; Queen Charlotte Fault (Canada’ equivalent of the San Andreas Fault); and Denali, Alaska. There has been active reconstruction of earthquake magnitudes, dynamics, and fault history based on comparisons with these analogs. Factors such as ground motion data, slip rate, max earthquake sizes, and occurrence of large earthquakes were also examined.
In particular, data from the 2011, Tohoku, Japan earthquake has been used to investigate ground motion that might occur for a potential future mega-thrust earthquake on Canada’s west coast. Researchers are examining if a similar earthquake in the offshore region of western Canada would lead to potentially damaging ground motion that might affect a long-term underground CO2 storage facility in Alberta.
Progress has also been made modeling earthquake ground motion based on a small set of statistically distributed design parameters. Extensive earthquake hazard analyses, performed by the team, have randomly generated synthetic ground motion for 1000’s of earthquakes to determine ground-motion effects.
A local earthquake catalog for Alberta and Canada is being created based on seismograph recordings. Preliminary PSHA maps have been prepared. An empirical approach has been developed to predict surface motion in relation to CCS storage depths.
The team is investigating reports for a magnitude 6.8 earthquake that occurred in Japan in 2004, in close proximity to an active CCS site. The engineers in Japan report there was negligible damage to the surface and underground infrastructure of the CCS project. The team is utilizing this information in their models.
Dr. David Eaton
Department of Geoscience
2500 – University Drive NW
University of Calgary
Calgary, AB, Canada T2N 1N4
T: 1 403 220 4275