It's Our Fault: Better Defining Earthquake Risk in Wellington

The It’s Our Fault programme aims to position Wellington to be 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. It’s Our Fault is jointly funded by New Zealand’s Earthquake Commission, Accident Compensation Corporation, Wellington City Council, Wellington Region Emergency Management Group, and Greater Wellington Regional Council. The programme comprises four main phases - Likelihood, Size, Effects and Impacts (Table 1), is currently in its fourth year of funding, and will be implemented over a seven year period. Work completed to date has largely focused on the Likelihood Phase which encompasses four themes (Table 1): 1) geological investigations to better constrain the location and rate of movement of major Wellington region faults, to extend the known sequence of surface rupture earthquakes, and to investigate evidence for large subduction thrust earthquakes; 2) GPS studies of the Wellington region to constrain the extent of the currently locked portion of the subduction thrust under Wellington; 3) synthetic seismicity modelling of the Wellington region to investigate the stress interactions of the major faults, and to specifically assess the rupture statistics and interactions of the Wellington-Wairarapa fault-pair; 4) evaluation of the conditional probability of rupture of the Wellington Fault. This paper presents a summary of some key results from these investigations, and an outline of the work plan for the Effects Phase currently underway.