ABSTRACT: Contemporary seismic hazard for the "stable" part of Canada.

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

About half of the Canadian landmass has too few earthquakes to define reliable seismic source zones; its previous seismic hazard came only from distant external sources. However, international examples suggest that large (M>6) earthquakes might occur anywhere in Canada, albeit rarely. Starting from the 1994 EPRI assessment of "Stable Continental Regions" we included only earthquakes from regions tectonically like the Canadian Shield. Just 66 earthquakes remained and passed completeness, with a well-defined magnitude-recurrence parameters of a0=273 p.a. per 10^6 km^2 and b=0.80. Upper bound magnitudes from this dataset suggest Mx not less than 7.0. The rate for North America alone is about 1/2 the global rate, suggesting that high-rate cratons like Australia dominate the global estimate. The rate for earthquakes in Canada outside our defined seismic source zones is 1/20 the global rate. To capture the uncertainty in seismicity rate all three rates were normalized by area and used as equally-weighted inputs. Uncertainty in upper-bound magnitude, depth and strong ground mothion relationships was also estimated. The hazard, using eastern strong ground motion relations, was then computed at the centre of a large octagonal source zone. Spectral results (in %g) for hard rock at the 2% in 50 year probability level (with 16th and 84th percentile range in brackets), are: PSA1.0=8.5 (2.1-21), PSA0.15=7.3 (2.6-17), PSA0.2=6.8 (2.4-16), PSA0.3=4.8 (1.7-13), PSA0.4=4.0 (1.2-10), PSA0.5=3.2 (0.9-8.8), PSA1.0=1.1 (0.3-4.6), PSA2.0=0.3, PGA=5.5 (1.3-14.3), PGV=0.021 (0.006-0.056). These hazard values have a large uncertainty, but the median values are expected to be the lowest hazard likely for any part of Canada, and so form an appropriate floor to Canadian building design levels.

Bibliography of Canadian Geomorphology