Earthquake hazard reports

All our reports on earthquake faults, earthquake shaking and liquefaction susceptibility across the region can be accessed below. 

Earthquake fault reports
Earthquake faults have been mapped at a scale of 1:250,000 for Kaikoura, Hurunui, Waimakariri, Selwyn, Ashburton, Timaru, Mackenzie, Waimate and Waitaki districts. These projects mapped earthquake faults that come up to the ground surface, so that future development near faults can be managed to reduce the risk of damage from surface fault rupture.
While Christchurch has experienced lots of earthquakes since 2010 none of the faults that created the earthquakes have cut all the way up to the ground surface so no report is planned for the Christchurch City Council area.

Some faults in Canterbury have been mapped in more detail (at scales of 1:50,000 or better), because they are close to developed areas. These include the Ashley Fault Zone in Waimakariri district, the Greendale Fault in Selwyn district, the Ostler Fault in Mackenzie district, the Hunters Hills Fault Zone in Waimate district. These reports are also available here (note that the Hunters Hills Fault Zone report has been superseded by the Waimate district fault report).

These district and detailed fault reports supersede our two older earthquake fault reports that covered the whole region - Earthquake Hazard and Risk Assessment Study: earthquake source identification and characterisation (1998) and Canterbury region earthquake source identification and characterisation (2008).

Earthquake shaking reports
Our earthquake shaking reports assessed how likely strong earthquake shaking is at different locations throughout Canterbury for 50, 150, 475 and 1000 year return periods – this is called the probabilistic seismic hazard (PSH).
The PSH is calculated by looking at the location of known earthquake faults, how often they are thought to move and how big an earthquake they could create, and adding in other possible earthquakes from as-yet unknown faults. GNS produced our first report in 1999 and updated it in 2007 with new fault information.

The earthquake shaking hazard for most of Canterbury has not changed since the 2007 report was produced, however the earthquake shaking hazard for the Canterbury earthquakes aftershock area (Rakaia Gorge to Banks Peninsula) is now higher than shown in the report over the next decade or so because of the 2010/11 earthquakes.

District earthquake hazard reports
Earthquake hazard assessments, focussed on the potential effects of earthquakes on infrastructure, were undertaken for Kaikoura, Hurunui, Waimakariri, Selwyn, Ashburton, Timaru, Mackenzie, Waimate and part Waitaki districts between 2000 and 2009.
These assessments include information on historic earthquakes, earthquake faults, expected earthquake shaking intensities for different time periods, general liquefaction susceptibility, and earthquake-induced landslide susceptibility. The later earthquake hazard assessments also include earthquake scenarios with possible short and long term impacts.

The Christchurch Engineering Lifelines Group (now the Canterbury Lifeline Utility Group) undertook a vulnerability assessment of Christchurch and Lyttelton’s infrastructure to several hazards in the mid-1990s and published the results as Risks and Realities in 1997.

Liquefaction reports 
Liquefaction susceptibility reports have been completed for eastern Canterbury (including Christchurch City and low-lying areas of Selwyn, Waimakariri and Hurunui districts), Hurunui district and Timaru district.
Liquefaction susceptibility maps for other districts are included in district earthquake hazard assessments.

The 2012 eastern Canterbury report replaced older liquefaction susceptibility reports for coastal Waimakariri (2000) and Christchurch (2005).

The liquefaction susceptibility reports outline broad zones where liquefaction is more or less likely to occur, and where site-specific geotechnical assessments may be needed.

None of the reports give the likelihood of liquefaction for a particular site or land parcel. This is because soil types can change a lot over very short distances - so soils on one property might be susceptible to liquefaction, while soils on the neighbouring property are not.