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It's Our Fault

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The goal of the It’s Our Fault programme is to see Wellington positioned to become a more resilient city through a comprehensive study of the likelihood of large Wellington earthquakes, the effects of these earthquakes, and their impacts on humans and the built environment.

The It’s Our Fault programme comprises three main phases: Likelihood, Effects and Impacts.

Likelihood Phase
Conducted between 2006 and 2010, the Likelihood Phase encompassed four themes:

Active faults of central New Zealand, including Cook Strait (Barnes & Pondard 2010; Pondard & Barnes 2010).

1) Geological investigations to better constrain the locations and rates of movement of major Wellington region faults, to extend the known sequence of surface rupture earthquakes, and to investigate evidence for large earthquakes on the subduction interface under Wellington.

2) GPS (geodetic) studies of the Wellington region to constrain the extent of the currently locked portion of the subduction interface under Wellington.

3) Computer modelling of Wellington region seismicity (synthetically generated) to investigate the stress interactions of the major faults in the region, and in particular to investigate whether or not rupture of the Wairarapa Fault enhances or retards the likelihood of rupture of the Wellington Fault.

4) Evaluate the likelihood of rupture of the Wellington Fault over the next several decades.

Subsoil class map of central Wellington (Semmens & Others 2011; Semmens et al_GNS CR 2010-176.pdf (6.58 MB) ).

Effects Phase
The underlying focus of the Effects Phase is better definition of earthquake ground shaking behaviour. Specific tasks within the Effects Phase, which commenced in 2008 and is on-going, include:

1) Geological and geotechnical characterisation of central Wellington, Lower Hutt and the wider region.

2) Seismic instrumentation of central Wellington and Lower Hutt to establish sediment material properties necessary for characterising earthquake ground shaking and liquefaction effects.

3) Characterisation of variations in ground shaking throughout the region, for example, through the mapping of subsoil classes according to the New Zealand Structural Design Standard

4) Characterisation and simulation of subduction interface earthquake motions.

5) Liquefaction hazard assessment.

6) Ground motion modelling, including comparison and integration of various ground motion estimation techniques over a range of shaking levels from weak to very strong.

Canterbury earthquake sequence.

Impacts Phase
For the impacts Phase, which started in 2010 and is on-going, earthquake vulnerability and risk will be assessed for the Wellington region – from an engineering as well as a social perspective. Both direct and indirect loss will be evaluated, and so too will wider impacts such as social dislocation and evacuation needs. The results from this work, when combined with other streams of investigation, will allow the identification of specific interventions that, if applied, will have the greatest impact towards increasing the region’s resilience to earthquakes.

Following the onset of the Canterbury earthquake sequence an additional component has been added to the Impacts Phase – an assessment of the potential impact of aftershocks and varying levels of moderate-size seismicity on hazard estimation in Wellington.

It’s Our Fault is jointly funded by New Zealand’s Earthquake Commission (EQC), Accident Compensation Corporation (ACC), Wellington City Council, Wellington Region Emergency Management Group, Greater Wellington Regional Council, and the Natural Hazards Research Platform.

IOF sponsors

It’s Our Fault is led by GNS Science, in collaboration with Massey University, NIWA, the University of Canterbury, and Victoria University of Wellington.

IOF collaborators

Russ Van Dissen
GNS Science
1 Fairway Drive, Avalon, Lower Hutt 5010
PO Box 30368, Lower Hutt 5040
New Zealand
T: +64 4 570 1444

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