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Abstract:
National-scale seismic hazard models with large logic trees can be difficult to calculate
using traditional seismic hazard software. To calculate the complete 2022 revision of the
New Zealand National Seismic Hazard Model—Te Tauira Matapae Pūmate Rū i
Aotearoa, including epistemic uncertainty, we have developed a method in which
the calculation is broken into two separate stages. This method takes advantage of logic
tree structures that comprise multiple, independent logic trees from which complete
realizations are formed by combination. In the first stage, we precalculate the independent
realizations of the logic trees. In the second stage, we assemble the full ensemble
of logic tree realizations by combining components from the first stage. Once all realizations
of the full logic tree have been calculated, we can compute aggregate statistics
for the model. This method benefits both from the reduction in the amount of computation
necessary and its parallelism. In addition to facilitating the computation of a large
seismic hazard model, the method described can also be used for sensitivity testing of
model components and to speed up experimentation with logic tree structure and
weights.
