Region-Specific Assessment, Adjustment, and Weighting of Ground-Motion Prediction Models: Application to the 2015 Swiss Seismic-Hazard Maps

摘要

We present a strategy for the region-specific assessment, adjustment, and weighting of ground-motion prediction models, with application to the 2015 Swiss national seismic-hazard maps. The models are provided within a logic-tree framework adopted for the probabilistic seismic-hazard analysis (PSHA). Through this framework, we consider both aleatory and epistemic uncertainties in ground-motion prediction in Switzerland, a region of low-to-moderate seismicity and consequently data poor in terms of strong-motion records. We use both empirical models developed using global strong-motion data and stochastic simulation models calibrated to local seismicity, characteristic wave-propagation effects, and site conditions. The empirical models were adjusted to account for (a) the selected hazard reference rock velocity model (using V-S-kappa(0) adjustments) and (b) the median instrumental ground-motion data at low magnitudes. The use of a carefully calibrated simulation model and V-S-kappa(0) adjusted empirical ground-motion prediction equations allowed us to precisely define the reference-rock profile, upon which subsequent analyses, such as microzonation and site-specific hazard, can be applied without uncertainty related to the reference condition. We implemented partially nonergodic aleatory uncertainties in ground-motion prediction through the single-station sigma approach. This strategy, complemented with the known reference rock condition, leads to significant reductions in the contribution of uncertainty in ground-motion characterization to PSHA in Switzerland. However, the application of the methodological framework outlined herein extends to any region, particularly those of low-to-moderate seismicity.