Seismic risk to pipelines with application to Northern Canada

Abstract

Proposed northern pipeline projects necessitate the estimation of seismic risk in the Arctic. Such estimates are difficult to obtain due to the lack of a good instrumental or historical data base, and the sparsity of tectonic information.Seismic risk estimates are commonly based on the procedures proposed by Milne and Davenport or those described by Cornell. The methods are inherently similar and the choice between the two is largely a matter of convenience. A modified Milne and Davenport approach (based on the amplitude recurrence distribution) appears to offer advantages in Northern Canada since it avoids the seismological problems of defining tectonic zones and maximum magnitudes.Uncertainties in the model assumptions are described by a factor having a log-normal distribution that modifies the predicted acceleration. The variability of the distribution can be adjusted regionally to reflect the quality and extent of seismic information.Seismically induced hazards to pipelines include overstressing due to travelling waves, liquefaction of silt-laden soils (possibly resulting in landslides), and abrupt displacement due to fault crossings. The potential for seismically induced liquefaction and for overstressing can also be evaluated probabilistically using modified forms of the amplitude recurrence distribution.