What we do.The Active Earth : GNS Science Limited

We are developing an integrated geological hazard model for New Zealand to estimate the future hazards that the country is likely to face. The general 4-Step methodology of probabilistic hazard analysis (Fig. 1) is being applied to this combined model. A probabilistic model uses information on where, how severe, and how often hazardous events (earthquakes, volcanic eruptions, landslides and tsunamis) occur, from historical and prehistorical (geologic) records of past events, to estimate the likely future levels of hazard at a given site for any user-specified time period. For earthquakes, the hazard is measured by the strength of shaking expected at the site in a specified time period; for volcanoes, the expected thickness of ashfall; for landslides, the expected size of landslide; and for tsunami, the maximum "runup" (water height) at the site. The ability to provide estimates of hazard for any user-specified time period makes probabilistic methods very useful to a variety of end-users.

For instance, planners and building engineers usually need to know the maximum strength of earthquake shaking expected in a 500 year timespan (i.e. 10% probability of exceedance in 50 years; Fig. 2), but a hydroelectric dam engineer can also use the same model to estimate the shaking expected in 10,000 years.

While our earthquake hazard model is currently the most advanced component of our integrated model, we have also undertaken some essential groundwork for the development of the other components.

For instance, in the volcanic component we have constructed eruption volume - frequency curves for some of the major volcanoes of New Zealand (Fig. 3), and equations that estimate the thickness of ashfall at some distance from an eruption. These developments have taken us through "Step 2" and "Step 3" of probabilistic hazard analysis (Fig. 1).

In addition to the development of a national probabilistic hazard model for New Zealand, we are also actively applying these methods to commercial projects in New Zealand and overseas.

Project Leader:
Mark Stirling
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Geological Hazard Models