Vulnerability to Liquefaction

Christchurch City Council commissioned Tonkin + Taylor to prepare a liquefaction vulnerability map which follows the most recent national liquefaction guidance. This map is available from https://apps.canterburymaps.govt.nz/ChristchurchLiquefactionViewer/.

The map uses the seven categories shown in the table below to describe the vulnerability of the land to liquefaction-induced damage. As well as describing the likelihood and severity of ground damage, the categories also show where there is more or less certainty about the ground conditions. For example, in some areas there is enough information to distinguish between areas of “Medium” and “High” vulnerability. But in other areas where there is less information it might only be possible to conclude that “Liquefaction Damage is Possible”. When more detailed information becomes available in future (e.g. new ground investigations), this might show that the actual vulnerability is “Medium” or “High”, or in some cases perhaps even “Low”.

There was already a substantial amount of previous information available about the liquefaction hazard in Christchurch, and the results of this latest assessment broadly align with what was previously known. This updated map makes improvements to the previous understanding of liquefaction vulnerability by:

Analysing the extensive collection of ground investigation data now available on the New Zealand Geotechnical Database.

Using observations of land damage caused by the Canterbury earthquakes to help calibrate predictions of future land damage.

Drawing on improved scientific understanding for analysis of liquefaction triggering and the resulting consequences.

Using the improved geology and groundwater maps that are now available, to better define areas of similar land performance.

Providing coverage of the entire Christchurch City territorial land area.

Using the consistent framework from the new national guidance to standardise the assessment methodology.

Data extracted from CCC June 2022.

Vulnerability to Liquefaction

Christchurch City Council commissioned Tonkin + Taylor to prepare a liquefaction vulnerability map which follows the most recent national liquefaction guidance. This map is available from https://apps.canterburymaps.govt.nz/ChristchurchLiquefactionViewer/.

The map uses the seven categories shown in the table below to describe the vulnerability of the land to liquefaction-induced damage. As well as describing the likelihood and severity of ground damage, the categories also show where there is more or less certainty about the ground conditions. For example, in some areas there is enough information to distinguish between areas of “Medium” and “High” vulnerability. But in other areas where there is less information it might only be possible to conclude that “Liquefaction Damage is Possible”. When more detailed information becomes available in future (e.g. new ground investigations), this might show that the actual vulnerability is “Medium” or “High”, or in some cases perhaps even “Low”.

There was already a substantial amount of previous information available about the liquefaction hazard in Christchurch, and the results of this latest assessment broadly align with what was previously known. This updated map makes improvements to the previous understanding of liquefaction vulnerability by:

Analysing the extensive collection of ground investigation data now available on the New Zealand Geotechnical Database.

Using observations of land damage caused by the Canterbury earthquakes to help calibrate predictions of future land damage.

Drawing on improved scientific understanding for analysis of liquefaction triggering and the resulting consequences.

Using the improved geology and groundwater maps that are now available, to better define areas of similar land performance.

Providing coverage of the entire Christchurch City territorial land area.

Using the consistent framework from the new national guidance to standardise the assessment methodology.

Data extracted from CCC June 2022.