| Title | Recent advances in long-term seismic monitoring and hazard assessment in northern Ontario |
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| Author | Ackerley, N; Kolaj, M; Peci, V; Adams, J |
| Source | 4th Canadian Conference on Nuclear Waste Management, Decommissioning and Environmental Restoration; 2019 p. 1-12 |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20200485 |
| Publisher | Canadian Nuclear Society |
| Meeting | 4th Canadian Conference on Nuclear Waste Management, Decommissioning and Environmental Restoration; Ottawa, ON; CA; September 8-11, 2019 |
| Document | computer file |
| Lang. | English |
| Media | digital |
| File format | pdf |
| Province | Ontario |
| NTS | 31; 32; 41; 42; 43; 44; 52; 53; 54 |
| Lat/Long WENS | -95.2500 -74.5000 55.0000 45.0000 |
| Subjects | geophysics; Science and Technology; Nature and Environment; Health and Safety; nuclear waste disposal; seismology; seismological network; seismicity; seismic risk; earthquake risk; earthquake
catalogues; earthquake magnitudes; bedrock geology; craton; models; Canadian National Seismograph Network; Canadian Shield; National Building Code of Canada (NBCC); monitoring |
| Illustrations | location maps; geoscientific sketch maps; time series; plots; histograms |
| Program | Canadian Hazard Information Service |
| Released | 2019 01 01 |
| Abstract | The safety case for a deep geological repository for high-level nuclear waste requires assessment of seismic hazard at very low probabilities, because the waste must remain sequestered for a million
years. Long-term seismic monitoring is required to estimate earthquake recurrence rates in regions of low seismicity. A program to monitor seismicity in the northern Ontario portion of the Canadian Shield was therefore established in 1982. The
catalogue produced, and continually improved, will be a key component of any seismic hazard assessment in this region. In 37 years, 1489 earthquakes have been catalogued with magnitude between 0.5 and 5.2, permitting accurate characterization of
present-day activity rates in several sub-regions. Until 2010, National Building Code of Canada (NBCC) modelled seismicity in the stable cratonic core of eastern Canada (SCCEC) based chiefly on activity rates in stable cratonic cores globally. The
model used by the 2015 NBCC introduced a source zone for the Severn Highlands (SVH). Activity rates in the SVH are slightly higher than the SCCEC, in line with models of cratonic regions globally. The model proposed for the 2020 NBCC incorporates
updated ground shaking intensity models that better represent short hypocentral distances and increase hazard at short periods. For some regions in northern Ontario the earthquakes are mainly shallow (1-6 km, e.g. SVH), while other regions have both
shallow and deep (10-18 km) earthquakes (e.g. under James Bay). The station distribution in northern Ontario is sparse relative to regions that are more seismically active. This has necessitated the development of new techniques for event depth
estimation. We evaluate the depth distributions used in the 2020 NBCC in light of the observed depths, the sensitivity of hazard to hypocentral depth, expected sources of error, and our knowledge of tectonic processes in the region. |
| Summary | (Plain Language Summary, not published)
The safety case for a deep geological repository for high-level nuclear waste requires assessment of seismic hazard at very low probabilities, because
the waste must remain sequestered for a million years. A program to monitor seismicity in the northern Ontario portion of the Canadian Shield was therefore established in 1982. One region currently under consideration for the siting of such a
repository is in the Severn Highlands (SVH). Seismicity rates in SVH are similar to stable continental cores globally, but the earthquakes are mainly shallow. We develop a seismic hazard model based on that proposed for the 2020 National Building
Code of Canada but with shallower depths. Our model predicts that ground motions will exceed 1.75 g an average of once per million years. At one standard deviation, this translates to 0.6-2.0 g. Our model can also serve as a baseline for future work
on other types of seismic hazard e.g. the likelihood of a rupture cutting directly through the repository. |
| GEOSCAN ID | 327397 |
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