A 3D Geological Model for Christchurch City (New Zealand): A Contribution to the Post-earthquake Re-build

Geological maps for areas of high density population play an important role in the design and planning of building and network infrastructure as well as management of subsurface resource such as groundwater and aggregate. The Christchurch urban area, New Zealand, experienced high ground shaking accelerations during the 2010-2011 Canterbury earthquake sequence (CES) and the built environment suffered serious damage from shaking and consequent liquefaction. Damage from the earthquakes focused efforts to improve understanding of materials and their properties beneath that city. This paper presents a summary of work undertaken to build a high resolution 3D geological model of these materials, including geomorphological mapping and analysis of materials using a large number of drillhole logs and digital cone penetration tests. An integrated 3D geological model and 3D numerical geotechnical models will contribute to the re-building of Christchurch and its infrastructure following the destructive earthquakes. Potential uses include planning optimal routing for major horizontal infrastructure (sewer, drainage and water supplies) where some foreknowledge of foundation conditions will allow re-alignment to easier substrates, more accurate cost estimates and more focused site specific foundation testing.