Seismic hazard analysis

Sponsors: NZ Earthquake Commission (EQC), Canterbury Earthquakes Royal Commission

Collaborators: Mark Stirling, Graeme McVerry, Matt Gerstenberger (GNS Science)

Postgraduate researchers: Varun Joshi, Karim Tarbali

Tectonic regionalization of New Zealand; and seismic hazard curve for Wellington NZ with epistemic uncertainty

New Zealand resides on the boundary of the Australian and Pacific plates and has a tectonic region governed by: (i) subduction of the Pacific plate in the Hikurangi margin to the east of the North Island (capable of Mw8.9); (ii) subduction of the Australian plate in the Fiordland (Puysegur) margin at the southwest of the South Island (Mw7.9 in 2009); and (iii) convergent right-lateral shallow crustal faults along the Axial Tectonic Belt, of which Alpine Fault is inferred to accomodate 70-75% of the plate boundary strain rate and produce earthquakes up to Mw8.1 every ~300 years.This work aims to improve the forecasting of seismic hazard for New Zealand, both via the official national-scale seismic hazard model (most recently Stirling et al. (2012)), and also site-specific seismic hazard analyses

Particular attention is given to strong Ground motion prediction, as well as the consideration of epistemic/modelling uncertainties, and their propagation to the seismic hazard estimates. The consideration of epistemic uncertainties allows for the identification of critical uncertainties which govern the percision of the analysis.

Guided by the results in Bradley et al. (2012), critical uncertainties for NZ-specific seismic hazard analyses include: (i) ground motion prediction via empirical prediction equations; (ii) magnitude-geometry scaling relationships; and (iii) rupture length, are critical uncertainties.

Current and future work is focusing on improved precision the above critical relationships, as well as the incorporation of additional uncertainties which were previously neglected, but which are known to be influential.

In order to improve the accessibility of seismic hazard analysis results to design engineers and public planners software tools for interogation of seismic hazard results are currently under development - keep an eye out on this page!