Consistency of groundmotion predictions from the

Authors: John Douglas

Publish Date: 2010/06/22

Volume: 8, Issue: 6, Pages: 1515-1526

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Abstract

Due to the limited observational datasets available for the derivation of groundmotion prediction equations GMPEs there is always epistemic uncertainty in the estimated median ground motion Because of the increasing quality and quantity of strongmotion datasets it would be expected that the epistemic uncertainty in groundmotion prediction related to lack of knowledge and data is decreasing In this study the predicted median ground motions from over 200 GMPEs for various scenarios are plotted against date of publication to examine whether the scatter in the predictions a measure of epistemic uncertainty is decreasing with time It is found that there are still considerable differences in predicted ground motions from the various GMPEs and that the variation between estimates is not reducing although the ground motion estimated by averaging median predictions is roughly constant For western North America predictions for moderate earthquakes have show a high level of consistency since the 1980s as do but to a lesser extent predictions for moderate earthquakes in Europe the Mediterranean and the Middle East A good match is observed between the predictions from GMPEs and the median ground motions based on observations from similar scenarios Variations in median ground motion predictions for stable continental regions and subduction zones from different GMPEs are large even for moderate earthquakes The large scatter in predictions of the median ground motion shows that epistemic uncertainty in groundmotion prediction is still large and that it is vital that this is accounted for in seismic hazard assessments

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