Earthquakes create a number of potential risks including ground shaking, liquefaction, land slips, tsunami and ground rupture.
Click here for the latest earthquakes.
Click here for earthquake hazard map
Click here for Earthquake Prone Dangerous & Insanitary Buildings Policy 2006
Fault Traces
In a major earthquake the ground may rupture, with ruptures typically occurring along existing fault traces. Therefore, any building built above a fault trace would be likely to be badly damaged.
To try and avoid any new buildings being constructed above the fault trace, the Council is proposing to alter the rules in the District Plan so that in most cases new buildings located above fault traces will require resource consent.
Where are the faults within the District?
The Institute of Geological and Nuclear Sciences (GNS) has mapped all of the known active fault traces within the Kapiti District. This information shows the likely location of the faults:
Map showing Kapiti's identified fault traces
It is possible that there are other faults within the District that have not yet been discovered. It is also possible that the fault information will become more precise over time, in which case the size of the Fault Trace Avoidance Zones shown on the map may be reduced.
View the location of the faults in relation to individual properties
Our GIS system shows this information graphically but please note you need to turn the ‘Fault Trace’ layer on – look under ‘Module’ for it.
Click here for the GNS Earthquake Fault Trace Study and additional information provided by GNS in 2007.
What are the risks associated with fault traces?
GNS has provided information on the average recurrence interval, which is the estimated average interval between ruptures on an individual section or length of a fault. Also presented below are its estimates on when the District's fault last ruptured.
For example, the Ohariu Fault has an estimated recurrence interval of between 1,300 and 3,800 years and a last rupture of approximately 1,000 years ago. This does not mean that there is no risk from fault rupture at present but based on the best information available there is a low risk.
Ohariu Fault: Has an average recurrence interval of surface rupture of 1,300 to 3,800 years. The fault most recently ruptured approximately 1,000 years ago. It is expected that an individual surface rupture along the fault could generate three to five metres of right-lateral displacement at the ground surface, with a lesser and variable amount of vertical displacement.
Northern Ohariu Fault: Has an average recurrence interval of surface rupture of 1,000 to 3,000 years. The fault most recently ruptured approximately 300-1,000 years ago. It is expected that an individual surface rupture along the fault could generate three to four metres of right-lateral displacement at the ground surface, with a lesser and variable amount of vertical displacement.
Gibbs Fault: The activity and location of the Gibbs fault is less well constrained than both the Ohariu and Northern Ohariu faults. There is currently no information of the average recurrence interval or on when the fault last ruptured and it is anticipated that the Gibbs fault would have a longer recurrence interval than the Ohariu or Northern Ohariu faults. A 3,500–5,000 year recurrence interval has therefore been estimated.
Otaki Forks Fault: The average recurrence and timing of faults on the Otaki Forks fault is unknown. However, a 3,500–5,000 year recurrence interval has been estimated and the potential surface rupture has been estimated to be approximately one metre.
Southeast Reikorangi Fault: This is the fault about which the least is known. It is estimated that the recurrence interval of this fault is 5,000–10,000 years.
Source: Institute of Geological and Nuclear Sciences' report 'Earthquake Fault Trace Survey Kapiti Coast District' (August 2003, updated August 2007).
If a fault does rupture any building located over the fault is likely to suffer significant damage, creating a risk for occupants. For example - using the Ohariu Fault again - GNS has estimated that a rupture could result in between three and five metres of right-lateral displacement, with less and more varied vertical displacement.
Because of this risk the Council is proposing to change the District Plan to minimise the number of new buildings located over fault traces.
There are a number of other risks associated with earthquakes including ground shaking, earthquake induced slope failure and liquefaction (in which the ground loses strength as a result of an earthquake, resulting in the slumping or rising of either the ground or buildings).
Each of these risks are likely to affect different areas within the District. According to the District Plan the areas most at risk from ground shaking are those over beach and dune sand, river and fan alluvium, and peat. This is typically the soil types in the coastal plains.
Liquefaction is identified in the District Plan as a risk in the Waikanae and Otaki areas but the risks are dependent on the ground conditions of particular sites.
Slope failure is also a risk most notably along the hills between Pukerua Bay and Paekakariki where the terrain is steep and the slopes have a high susceptibility to slope failure.
Although the Council is currently undertaking a Plan Change in relation to fault traces, it is important to be aware that there are a number of risks associated with earthquakes which affect different areas of the District.
Map showing risks of the different earthquake hazards to different areas of Kapiti
What are the changes proposed to the District Plan?
Changes are proposed which will affect subdivisions and new buildings in the Residential and Rural zones of the District:
Proposed Plan Changes (6 pages, 80kb)
Planner's Report (13 pages, 457kb)
This report provides the justification for the Plan Change
In summary the Plan Change will make the following changes:
Subdivision:
• If a 200m2 building platform is provided clear of the fault trace avoidance zone then the subdivision of the site will be dealt with in the same way as it would have been previously.
• If a 200m2 building platform can not be provided clear of the fault trace avoidance zone then the Council will take into consideration the risk that the fault poses, and may request additional information. For example, the Council may request the applicant to undertake geotechnical works such as trenching to more accurately locate the fault.
Constructing a new building or extending an existing building:
• Resource consent would not be required for sheds and other non-habitable structures, including extensions to buildings where the rooms are ‘non-habitable’ such as laundries and bathrooms, unless the proposal does not comply with some other rule in the District Plan.
• Dwellings and extensions of habitable rooms such as bedrooms and living rooms. Resource consent would be required and would be classed as a Limited Discretionary Activity. Consideration would be given to:
- whether the building could be located away from the fault trace;
- the risks associated with the fault trace; and
- the design of the building or extension, e.g. whether the building was one or two storeys, or made of lightweight materials.
NB: There is one exception to this in which resource consent is not required where a dwelling, or an extension to a dwelling, is proposed over an 'Uncertain-Poorly Constrained' fault (unless the proposal does not comply with some other rule in the District Plan).
• Commercial and industrial buildings, community facilities and buildings used for the storage of hazardous substances:
Resource consent would be required for a Non-Complying Activity.
The proposed Plan Change was publicly notified on 16 November 2007. The proposed changes will be taken into consideration once the Plan Change has been notified, along with the existing rules.
Make a submission on the proposed Plan Change