Mapping liquefaction vulnerability for Christchurch City

Following the Christchurch earthquakes of 2010-2011 Tonkin + Taylor performed a large amount of geotechnical analysis for Christchurch City Council (CCC) and Environment Canterbury (ECan) to better understand possible liquefaction-induced damage under future earthquake events. Liquefaction is a natural process where earthquake shaking increases the water pressure in the ground causing some soils to behave like a fluid, resulting in temporary loss of soil strength. As shown by the Canterbury earthquakes it can cause significant damage to land, buildings, and infrastructure, through sediment being ejected to the ground surface, and subsequent ground settlement, ground cracking and lateral spreading. The geotechnical modelling included predictive assessments of liquefaction damage under various scenarios of earthquake intensity and groundwater level.

To assist in publicly disseminating this information the software development team at Abley collaborated with Tonkin + Taylor to develop a new website that presents information about the liquefaction hazard in Christchurch City. The Christchurch Liquefaction Information viewer enables the public to explore how the soils, magnitude and location of an earthquake and groundwater levels can affect likely patterns of land damage, and presents other relevant contextual information, such as historical imagery and data dating back to 1856. Most of this information is not new, but it is now all gathered in one place, making it easier to access. This information can be important when deciding how to construct buildings and infrastructure, and when planning for future development of the city.

The website consists of 6 key components: 

• It explains how liquefaction occurs and its consequences
• The Liquefaction Lab allows experimentation with different scenarios to see how these impact liquefaction damage.
• A vulnerability map showing how liquefaction vulnerability varies across Christchurch.
• Earthquake maps showing observations from the 2010-2011 Canterbury earthquakes.
• General contextual maps about ground conditions across Christchurch such as land category, groundwater, surface elevation, historical or geomorphic features.
• Compare map functionality, which allows any two of these maps to be placed side-by-side and compared using a slider tool.

Watch this short YouTube video: