Attenuation relations for strong seismic ground motion in Canada

Abstract

Abstract Strong seismic ground motion attenuation relations based primarily on Western United States data, in conjunction with intensity data from eastern and western Canada, are employed to derive new attenuation relations for horizontal strong seismic ground motion for application throughout Canada. The following peak acceleration (ap) and peak velocity (vp) relations are proposed for use in western Canada a p ( cm sec − 2 ) = 10 e 1.3 M R − 1.5 v p ( cm sec − 1 ) = 0.00040 e 2.3 M R − 1.3 where M is magnitude and R hypocentral distance (km). The difference in the distance attenuation of Modified Mercalli intensity in eastern and western Canada, and an assumption of equivalent strong motion in the near field in the two regions, is applied to the western relations to derive the following relations proposed for use in eastern Canada a p ( cm sec − 2 ) = 3.4 e 1.3 M R − 1.1 v p ( cm sec − 1 ) = 0.00018 e 2.3 M R − 1.0 . The proposed relations are in reasonable agreement with the small amount of strong motion data available for western and eastern Canada. Within the accuracy justified by very scattered experimental data, peak vertical and sustained horizontal acceleration and velocity can be estimated as 23 of the peak horizontal values. The magnitude and distance dependence of acceleration and velocity parameters are sufficiently different that the relative levels of ground motion bounds in different frequency ranges will depend on the dominant magnitudes of, and distance ranges to, the earthquakes contributing risk in various regions of Canada. The results indicate the importance of mapping risk for parameters in addition to simple peak acceleration, and suggest alternative methods of deriving ground motion bounds required for the development of design response spectra.