Is Our True Understanding of Earthquake Occurrence Reflected in Modern Building Codes?

Abstract eng:
For more than 20 years, the New Zealand National Seismic Hazard Model (NSHM) has been constructed using the standard methods of probabilistic seismic hazard assessment. In this approach a source model is first constructed by combining models developed from earthquake catalogue data and active fault data; these models are assumed to be Poissonian in nature. The combined source model is then coupled with ground-motion prediction equations (GMPEs) to estimate the potential shaking at desired locations. In recent years, there has been considerable progress and improvement in understanding of the uncertainties inherent in GMPEs. In our current work, we are revisiting some of the fundamental assumptions of the NSHM and investigating how both model and parameter uncertainties in the earthquake source and ground motion modelling propagate through to the end uses of the model. In New Zealand, a major end-use is the development of anti-seismic provision in the national building design standards. Some uncertainties are not quantified in the present model. These include uncertainties resulting from a paucity of earthquake occurrence data and from different methods that can be used to model the seismic sources. Also the stationary Poisson asumption ignores the known clustering of earthquakes in time and space. This paper will explore the impact of including these uncertainties in the NSHM on downstream risk-based applications of the model, with a view to more robust estimates of risk for use by industry and in the development of design standards.

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