| Title | Seismic hazard in western Canada from global positioning system vs. earthquake catalogue data |
| Author | Mazzotti, S; Leonard, L J; Cassidy, J C; Rogers, G; Halchuk, S |
| Source | 2010 Annual Seismological Society of America Meeting, Abstracts; Seismological Research Letters vol. 81, no. 2, 2010 p. 364 |
| Year | 2010 |
| Alt Series | Earth Sciences Sector, Contribution Series 20100153 |
| Meeting | 2010 Annual Seismological Society of America Meeting; Portland; US; April 21-23, 2010 |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| Province | Alberta; British Columbia |
| Subjects | geophysics; earthquakes; earthquake catalogues; earthquake studies; global positioning system |
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| Program | Targeted Hazard Assessments in Western Canada, Public Safety Geoscience |
| Links | Online - En ligne
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| Abstract | Probabilistic seismic hazard analyses are principally based on frequency-magnitude statistics of historical and instrumental earthquake catalogues. This method assumes that return periods of large
damaging earthquakes (100s - 1000s yr) can be extrapolated from 50-100 yr statistics of small and medium earthquakes. The method has obvious limitations when applied to areas of low-level seismicity where the earthquake statistics may be poorly
constrained. In this study, we test an alternative approach to assess seismic hazard in Western Canada. We use horizontal velocities at ~250 Global Positioning System (GPS) sites in BC and Alberta to calculate strain rates and earthquake statistics
within seismic source zones. GPS-based strain rates are converted to seismic moment, earthquake frequency-magnitude statistics, and seismic hazard using a logic-tree method. The GPS-based earthquake statistics and seismic hazard are then compared to
those derived from the earthquake catalogue. In one zone (Puget Sound), the GPS seismic hazard estimates are in good agreement with those from earthquake statistics. In nearly all other zones (e.g., most of BC and Alberta), the GPS seismic hazard
estimates are significantly larger than those from the earthquake catalogue by one or two orders of magnitude. This discrepancy could indicate that the earthquake catalogue significantly under predicts long-term seismic hazard in areas of low-level
seismicity. Alternatively, significant aseismic deformation may occur over long time-scales, which would imply that the GPS strain rates over predict the true seismic hazard. We discuss the nature and limitations of both methods in light of our
results for Western Canada, with the goal of defining a methodology to incorporate GPS strain rate data into probabilistic seismic hazard assessments. |
| GEOSCAN ID | 286198 |
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