New Zealand Seismic Hazard Z Factors

This dataset presents our interpretation of the Z factor as a continuous surface across New Zealand. The GeoTiFF has been derived through a range of publicly available online resources including the MBIE website, reports, journal publications, and the New Zealand Gazetter for matching placenames to locations, amongst others. The coordinate system is EPSG:2193 with ~5 km resolution. The raster has a single band and values are rounded to two decimal places.

The Z factor is used to scale the 5% damped design seismic response spectrum based on the magnitude of the expected seismic hazard in different regions in New Zealand, as demonstrated through NZS 1170.5:2004 and referred to in the seismic assessment of potentially earthquake prone buildings (EPB). It is underpinned by the 2001 National Seismic Hazard Model and is influenced by a wide range of factors such as proximity to faults and fault rupture mechanisms, geological and soil characteristics, and topography, amongst others. Z ranges from 0.10 (Northland Region) to 0.60 (Otira/Arthur’s Pass surrounds). Generally speaking, low seismic risk is where Z < 0.15; medium seismic risk where 0.15 ≤ Z < 0.30; and high seismic risk where Z ≥ 0.30.

This GIS dataset is intended for educational purposes where students can download the dataset, create their own contours, or directly sample the raster. For more information see the numerous online resources and the official standard NZS 1170.5:2004 where it is available for purchase from Standards NZ.