Introduction

Canterbury is vulnerable to geological hazards including earthquakes, tsunamis and landslides.  We can’t stop earthquakes and tsunamis from happening, but we can reduce their impacts (including ground shaking, ground deformation, landslides, liquefaction and flooding) by:

• making sensible land use decisions.
• keeping natural defences such as sand dunes intact.
• designing and constructing strong buildings.
• having warning systems in place where possible.
• being prepared at home, work and school.

Geological hazard information given on Land Information Requests

• Known earthquake faults on the property which could move, generating an earthquake and permanently displacing land across the fault.
• Other nearby faults that are capable of generating damaging earthquakes.
• The likelihood of ground shaking in the area (taking into account all known nearby faults, how often on average they generate earthquakes, and the size of those earthquakes).
• Whether soils in the area may amplify earthquake shaking (where information is available).
• Liquefaction potential (where information is available).
• Landslide hazard (where relevant and where information is available).
• Tsunami hazard (for coastal properties where information is available).

Geological hazard information held by Environment Canterbury

Earthquake source (fault) information

We hold information on the location and characteristics of known earthquake faults in and near Canterbury.  These faults are capable of generating damaging earthquakes, with permanent horizontal and/or vertical displacement of land across the fault trace (the line where the fault meets the ground surface).  The accuracy of fault trace locations depend on the scale they were mapped at, which varies throughout the region.  Most of the fault traces in the region are mapped at 1:250,000 or 1:50,000 scale.  A few fault traces have been mapped at scales of less than 1:20,000.  Information on fault type, slip rate, average displacement and recurrence interval (average time between fault movements) is available for most of the faults, and information on the timing of the last earthquake on the fault is available for some. 

Ground shaking hazard information

We hold information on the level of ground shaking expected in Canterbury for 50, 150, 475 and 1000 year return periods.  This probabilistic ground shaking information is derived from modelling the likely frequency and size of earthquakes that may be generated by 133 known earthquake faults in and near Canterbury, along with historic seismicity. 

Modified Mercalli (MM) intensity, peak ground acceleration and spectral acceleration is available at a regional scale, and also specifically for the urban areas of Kaikoura, Hanmer Springs, Arthur’s Pass, Rangiora, Kaiapoi, Christchurch, Ashburton, Temuka, Timaru, Twizel and Waimate.

The probabilistic ground shaking modelling assumes uniform geology and soil type across the region.  In reality, local conditions such as soil type and depth, as well as local topography, can either amplify or lessen the level of ground shaking at a particular location.  District-scale information on areas where ground shaking may be amplified by local variations in soil type is available for Kaikoura, Waimakariri, Selwyn, Ashburton, Timaru, Mackenzie, Waimate and part-Waitaki districts.

Liquefaction information

Liquefaction is a process that causes some soils to lose their strength and behave more like a liquid than a solid during a strong earthquake shaking. It only occurs in unconsolidated (loose) soils that are saturated (below the water table).

District-scale information on the liquefaction potential of soils is available for Kaikoura, Waimakariri, Selwyn, Ashburton, Timaru, Mackenzie, Waimate and part-Waitaki districts.  Information is also available for the urban area of Christchurch city, and settlements around Akaroa Harbour.  We do not hold any site-specific (property level) liquefaction information. More details on liquefaction information for Christchurch can be found here:

The Solid Facts on Christchurch Liquefaction (pdf 1.91 MB)

Tsunami hazard information

Some tsunami scenarios have been modelled for parts of the Canterbury coast.  Limited tsunami hazard information is available for the Kaikoura, Hurunui, Christchurch, Akaroa Harbour, and Timaru coasts. 

Landslide hazard information

District scale information on earthquake-induced landslide potential is available for Kaikoura, Waimakariri, Selwyn, Ashburton, Timaru, Mackenzie, Waimate and part-Waitaki districts.  Some landslide hazard information is also available for the Port Hills area of Christchurch and the settlement areas of the Akaroa Harbour basin.

Historic information

We hold information on historic earthquakes and tsunamis that have affected the Canterbury region, including:

• 1868 Arica (Peru) tsunami
• 1869 New Brighton earthquake (magnitude ~5.0)
• 1870 Lake Ellesmere earthquake (magnitude 5.5)
• 1877 Northern Chile tsunami
• 1881 Castle Hill earthquake (magnitude 6.2-6.3)
• 1888 North Canterbury earthquake (magnitude 7.0-7.3)
• 1901 Cheviot earthquake (magnitude 6.5-7.0)
• 1922 Motunau earthquake (magnitude 6.5-6.7)
• 1929 Arthur’s Pass earthquake (magnitude 7.1)
• 1960 Chile tsunami
• 1994 Arthur’s Pass earthquake (magnitude 6.7)
• 1995 Cass earthquake (magnitude 6.3)

Earthquake scenarios

We have information on the potential impact of selected earthquake scenarios including Alpine Fault, Ostler Fault, Hunters Hills Fault, Canterbury Range Front Fault, Porters Pass-Amberley Fault Zone and Hope Fault earthquakes.

Other data

Your city or district council may hold more detailed geological hazard information for the site of interest, or nearby sites.

Limitations of data

1. The geological hazard information held by Environment Canterbury is gathered at a regional or district scale and is indicative only.  Only a site-specific investigation by a suitably qualified and experienced geologist or engineer can determine the potential for damage on a particular property from geological hazards.
2. The geological hazard information held by Environment Canterbury is based on the best information available at the time it was collected.  It is generally supplied to Environment Canterbury under specific contract arrangements including financial and time constraints.
3. The geological hazard information held by Environment Canterbury may be liable to change or review if new information becomes available.