A Line of Best Fit explores weakness and disconnection in the city. Weakness: There are over 600 earthquake prone buildings in Wellington. The urgency to strengthen buildings risks compromising the aesthetic integrity of the city through abrasive strengthening techniques, or losing a large portion of our built environment to demolition. The need for extensive earthquake strengthening in Wellington, Christchurch and other New Zealand cities provides an exciting opportunity for architecture. Disconnection: In Wellington pedestrian activity is focused around three main routes: Cuba Street, Lambton Quay and Courtney Place. The adjacent areas are often disconnected and lack vibrancy due to large building footprints, no-exit laneways and lack of public spaces. The Design proposes a strategy for earthquake strengthening, preserving and upgrading the built environment, and expanding and connecting the pedestrian realm. The site is two earthquake prone buildings on the block between Marion Street and Taranaki Street in central Wellington. A cut through the centre of the Aspro and Cathie Buildings ties the buildings together to strengthen and create a new arcade as public space. The cut aligns with existing pedestrian routes connecting the block with the city. The Design is divided into three components: Void, Curve, and Pattern and Structure. Void investigates the implications of cutting a portion out the existing buildings and the opportunities this provides for connection, urban interaction, and light. Curve discusses the unusual form of The Design in terms of scale, the human response and the surrounding spaces. Pattern and Structure considers the structural requirements of the project and how a void enveloped in perforated screens can strengthen the earthquake prone buildings. The importance of connection, providing strength in the city, a dialogue between old and new, and engagement with the unexpected are evaluated. Opportunities for further development and research are discussed, with particular reference to how the principles of The Design could be implemented on a larger scale throughout our cities. A Line of Best Fit is an architectural proposal that creates strength and connection.
Earthquakes are insured only with public sector involvement in high-income countries where the risk of earthquakes is perceived to be high. The proto-typical examples of this public sector involvement are the public earthquake insurance schemes in California, Japan, and New Zealand (NZ). Each of these insurance programs is structured differently, and the purpose of this paper is to examine these differences using a concrete case-study, the sequence of earthquakes that occurred in the Christchurch, New Zealand, in 2011. This event turned out to have been the most heavily insured earthquake event in history. We examine what would have been the outcome of the earthquakes had the system of insurance in NZ been different. In particular, we focus on the public earthquake insurance programs in California (the California Earthquake Authority - CEA), and in Japan (Japanese Earthquake Reinsurance - JER). Overall, the aggregate cost to the public insurer in NZ was $NZ 11.1 billion in its response to the earthquakes. If a similar-sized disaster event had occurred in Japan and California, homeowners would have received $NZ 2.5 billion and $NZ 1.4 billion from the JER and CEA, respectively. We further describe the spatial and distributive patterns of these different scenarios.
Located on the edge of two tectonic plates, New Zealand has numerous fault lines and seismic risk across the whole country. The way this risk is communicated affects whether people prepare effectively or at all. Research has shown that perceptions of risk are affected by slight changes in wording, and that probabilities commonly reported by experts and media are often interpreted subjectively based on context. In the context of volcanoes, research has found that given a certain probability of a volcano in a specific time window, people perceive risk as higher in later time intervals within that window. The present study examines this pattern with regard to earthquakes and aftershocks in the New Zealand context. Participants in both Wellington (N = 102) and Christchurch (N = 98) were presented an expert statement of earthquake risk within a given time window in Wellington and aftershock risk in Christchurch, and asked to rate their perception of risk in specific intervals across the time window. For a Wellington earthquake, participants perceived risk as incrementally higher toward the end of the 50 year time window whereas for a Christchurch aftershock, risk perception increased slightly for the first three intervals of the 12 month time window. Likelihood of preparing was constant over the time windows, with Wellington citizens rating themselves more likely than Christchurch citizens to prepare for either an earthquake or aftershock, irrespective of current level of preparedness. These findings suggest that people view earthquakes as more likely later toward the end of a given time window and that they view aftershocks very differently to scientific predictions.
The last seven years have seen southern New Zealand a ected by several large and damaging earthquakes: the moment magnitude (MW) 7.8 Dusky Sound earthquake on 15 July 2009, the MW 7.1 Dar eld (Canterbury) earthquake on 4 September 2010, and most notably the MW 6.2 Christchurch earthquake on 22 February 2011 and the protracted aftershock sequence. In this thesis, we address the postseismic displacement produced by these earthquakes using methods of satellite-based geodetic measurement, known as Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS), and computational modelling. We observe several ground displacement features in the Canterbury and Fiordland regions during three periods: 1) Following the Dusky Sound earthquake; 2) Following the Dar eld earthquake and prior to the Christchurch earthquake; and 3) Following the Christchurch earthquake until February 2015. The ground displacement associated with postseismic motion following the Dusky Sound earthquake has been measured by continuous and campaign GPS data acquired in August 2009, in conjunction with Di erential Interferometric Synthetic Aperture Radar (DInSAR) observations. We use an afterslip model, estimated by temporal inversion of geodetic data, with combined viscoelastic rebound model to account for the observed spatio-temporal patterns of displacement. The two postseismic processes together induce a signi cant displacement corresponding to principal extensional and contractual strain rates of the order of 10⁻⁷ and 10⁻⁸ yr⁻¹ respectively, across most of the southern South Island. We also analyse observed postseismic displacement following the Dusky Sound earthquake using a new inversion approach in order to describe afterslip in an elasticviscoelastic medium. We develop a mathematical framework, namely the "Iterative Decoupling of Afterslip and Viscoelastic rebound (IDAV)" method, with which to invert temporally dense and spatially sparse geodetic observations. We examine the IDAV method using both numerical and analytical simulations of Green's functions. For the post-Dar eld time interval, postseismic signals are measured within approximately one month of the mainshock. The dataset used for the post-Dar eld displacement spans the region surrounding previously unrecognised faults that ruptured during the mainshock. Poroelastic rebound in a multi-layered half-space and dilatancy recovery at shallow depths provide a satisfactory t with the observations. For the post-Christchurch interval, campaign GPS data acquired in February 2012 to February 2015 in four successive epochs and 66 TerraSAR-X (TSX) SAR acquisitions in descending orbits between March 2011 and May 2014 reveal approximately three years of postseismic displacement. We detect movement away from the satellite of ~ 3 mm/yr in Christchurch and a gradient of displacement of ~ 4 mm/yr across a lineament extending from the westernmost end of the Western Christchurch Fault towards the eastern end of the Greendale East Fault. The postseismic signals following the Christchurch earthquake are mainly accounted for by afterslip models on the subsurface lineament and nearby faults.
