© 2017 The Royal Society of New Zealand. This paper discusses simulated ground motion intensity, and its underlying modelling assumptions, for great earthquakes on the Alpine Fault. The simulations utilise the latest understanding of wave propagation physics, kinematic earthquake rupture descriptions and the three-dimensional nature of the Earth's crust in the South Island of New Zealand. The effect of hypocentre location is explicitly examined, which is found to lead to significant differences in ground motion intensities (quantified in the form of peak ground velocity, PGV) over the northern half and southwest of the South Island. Comparison with previously adopted empirical ground motion models also illustrates that the simulations, which explicitly model rupture directivity and basin-generated surface waves, lead to notably larger PGV amplitudes than the empirical predictions in the northern half of the South Island and Canterbury. The simulations performed in this paper have been adopted, as one possible ground motion prediction, in the ‘Project AF8’ Civil Defence Emergency Management exercise scenario. The similarity of the modelled ground motion features with those observed in recent worldwide earthquakes as well as similar simulations in other regions, and the notably higher simulated amplitudes than those from empirical predictions, may warrant a re-examination of regional impact assessments for major Alpine Fault earthquakes.
This article presents a quantitative case study on the site amplification effect observed at Heathcote Valley, New Zealand, during the 2010-2011 Canterbury earthquake sequence for 10 events that produced notable ground acceleration amplitudes up to 1.4g and 2.2g in the horizontal and vertical directions, respectively. We performed finite element analyses of the dynamic response of the valley, accounting for the realistic basin geometry and the soil non-linear response. The site-specific simulations performed significantly better than both empirical ground motion models and physics based regional-scale ground motion simulations (which empirically accounts for the site effects), reducing the spectral acceleration prediction bias by a factor of two in short vibration periods. However, our validation exercise demonstrated that it was necessary to quantify the level of uncertainty in the estimated bedrock motion using multiple recorded events, to understand how much the simplistic model can over- or under-estimate the ground motion intensities. Inferences from the analyses suggest that the Rayleigh waves generated near the basin edge contributed significantly to the observed high frequency (f>3Hz) amplification, in addition to the amplification caused by the strong soil-rock impedance contrast at the site fundamental frequency. Models with and without considering soil non-linear response illustrate, as expected, that the linear elastic assumption severely overestimates ground motions in high frequencies for strong earthquakes, especially when the contribution of basin edge-generated Rayleigh waves becomes significant. Our analyses also demonstrate that the effect of pressure-dependent soil velocities on the high frequency ground motions is as significant as the amplification caused by the basin edge-generated Rayleigh waves.
Under the framework of New Public Management, the government has decentralised the responsibility for Disaster Risk Management (DRM) to regional, local, and community levels in New Zealand. This decentralisation serves political agendas related to resource allocation and is supported by empirical evidence suggesting that involving communities in DRM during recovery decision-making enhances disaster resilience. Extensive evidence indicates that community participation in DRM, especially during recovery decision-making, can significantly improve recovery outcomes at the community level. However, there has been limited research into whether the legal framework in New Zealand effectively facilitates meaningful public engagement to empower the public in influencing disaster recovery decisions. To address this gap in the literature, this thesis aims to explore the extent to which legislative and governance arrangements transfer the responsibility, liability, and costs of managing disaster risks to local levels without enabling meaningful public contribution to and influence on recovery decisions affecting them. Situated within Public Law and Disaster Risk and Resilience disciplines and using a case study of Greater Christchurch, New Zealand, this interdisciplinary thesis examines both common law and statutory provisions in the legal framework impacting public engagement before and during recovery from the Canterbury Earthquake Sequence. In particular, this thesis assesses how legislative, and governance frameworks influenced communities’ ability to influence recovery decision-making following the 2010-2011 Canterbury Earthquake Sequence (CES). This thesis shows that before the CES, the New Zealand public engagement system closely adhered to the common law principle of the ‘duty to consult’, which remains the current legal standard. This principle required decision-makers to use the 'public notice and comment' approach as a minimum, limiting meaningful community participation in decision-making. After the earthquakes, reliance on this traditional approach caused growing frustration and division locally, as the public struggled to effectively engage in and influence recovery decisions, resulting in new community activism. The Canterbury Earthquake Recovery Act (CER Act), introduced following the Christchurch Earthquake, included innovative provisions on public engagement. However, for various reasons, this Act appeared to have minimal impact on meaningful public engagement in recovery decision-making, which continued to align with the broader, existing public engagement system and associated norms. The empirical findings indicate that despite the novel legislative language, the traditional public engagement framework in New Zealand constrained effective engagement, leading to a broader erosion of trust between the public and the government. This was largely attributed to the default ‘public notice and comment’ approach at the local government level, with inadequate mechanisms for community engagement in central government decision-making shaping the expectations of recovery decision-makers still operating within this framework. Notable departures from this traditional approach were evident in the practices of the Waimakariri District Council and Christchurch City Council. Particularly noteworthy was the ‘Share an Idea’ public engagement campaign. Unlike conventional processes, it did not commence with a near-final or draft document. Instead, it utilised participatory mechanisms that fostered meaningful dialogue, enabling the public to significantly shape the content of the draft Christchurch Central Recovery Plan. The initial success of such participatory engagement underscores its potential effectiveness throughout the entire recovery planning process, an option that was not exercised by the central government. In conclusion, this thesis argues that New Zealand should move beyond the entrenched ‘public notice and comment’ approach and adopt more open and inclusive public participation mechanisms. It contends that supplementing this approach with proactive participatory methods before disasters could yield favorable outcomes during disaster recovery, thereby ensuring meaningful public involvement in future decisions that affect communities.
