A ground shaking amplification map for New Zealand
A ground shaking amplification map of New Zealand has been compiled from data held by GNS Science. The resulting map is being used in RiskScape, a tool for comparing risks at a given site from a variety of hazards by estimating potential losses.
A GIS-based geological map with national coverage has been composed from several sources, and is used as the base data. Geological maps from the QMAP project (an ongoing project to digitally compile 1:250,000 geological maps for all of New Zealand) have been used where available, supplemented with detailed geological maps at scales ranging from 1:25,000 to 1:50,000 for the larger urban areas. Gaps in the QMAP series have been filled by the 1:1,000,000 ‘Geological Map of New Zealand’.
Every geological polygon in the composite geological map has been assigned one of the ground shaking amplification (or site) classes from the New Zealand Standard for Structural Design Actions – Earthquake actions (NZS 1170.5) to produce the result map. These conform to the site class definitions in NZS 1170.5, which describes five classes with respect to ground shaking amplification. Assignment of these classes was straightforward for rock sites but more involved for soils where, for example, at boundaries between weak rock and deep soil sites a buffer zone of shallow soil was applied.
Cousins, J.W., Barker, P., Perrin, N.D., McVerry, G. H., ‘Compilers’ Unpublished GNS accelerograph locations and information database.
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