Understanding non-elastic effects in accretionary wedges using the Kaikoura earthquake: Investigating a major potential tsunami hazarard

当地震发生时，储存在经历逐渐分布变形的岩石中的弹性能突然沿着一个或多个被称为断层的平面不连续面释放出来。根据定义，故障是非弹性的，因为它们释放了储存的弹性能量，使损伤局部化。然而，如果断层两侧的岩石没有受到严重破坏，则可以使用从野外观测、InSAR或其他技术确定的水平和垂直同震地表运动来构建弹性半空间模型，该模型可以预测断裂面上全深度范围内滑动的方向和大小。然而，在某些情况下，这些模型会受到岩体非弹性行为的影响，导致地表破裂结果不一致，并且在深度滑动估计中可能出现重大误差。这种意义上的非弹性作用可能是由次级断裂的运动、岩层的褶皱、软变形带的形状变化以及韧性下地壳的粘弹性变形引起的；这些影响最明显地体现在地震后的运动中，通常在大地震后的几天到几个月里观察到，也体现在位于主断层附近的余震中。提高我们对这些影响的理解是很重要的，因为断层滑动和地震震级之间的关系构成了地震危害分析的重要组成部分。在这种情况下，改进我们的2016年凯库拉地震中所有断层的滑动模型将增强该地区的地应力积累模型，这是改进中短期地震预报和地震危险性分析的关键。此外，进一步了解位于俯冲界面上方的增生棱镜的机制，对于理解新西兰和其他地区的海啸产生具有重要意义。我们有机会利用新加坡地球观测站（EOS）（新加坡南洋理工大学研究所）在3d应变建模领域取得的最新重大概念和处理进展。由Sylvain Barbot助理教授领导的团队将地球物理和数学技能结合起来，开发了一种模拟地壳变形复杂性的方法，该方法的计算效率明显高于以前的数值方法。这是一个前所未有的机会，可以利用2016年11月14日非常大而复杂的凯库拉地震，详细研究增生楔如何随着构造板块的位置调整形状，以及大陆-海洋边缘的不同组成部分如何随着时间的推移而演变。作为我们正在进行的NERC紧急奖（NE/P021425/1）的一部分，我们收集的高质量数据使这对EOS研究团队来说是一个有吸引力的研究合作，而对我们来说，它大大扩展了我们项目的范围，提供了利用我们的结果在断层运动，地震发生和景观演化的基本行为方面发展重大发现的机会。这将为现有的nerc资助项目增加重大价值，并形成长期研究合作的基础，同时为地震危害分析提供重要的新信息，帮助建立抵御自然灾害的能力。

When an earthquake occurs, elastic energy that has been stored in rocks that have been undergoing gradual distributed deformation is released suddenly along one or more planar discontinuities known as faults. By definition faults are non-elastic, as they relieve stored elastic energy, localising damage. However, where the rocks on either side of the fault are not significantly damaged, horizontal and vertical coseismic surface movement determined from field observations, InSAR, or other techniques may be used to construct an elastic half-space model that predicts the direction and magnitude of slip at a full range of depths on the fault plane. However, in some cases these models are compromised by non-elastic behaviour of rock bodies, leading to inconsistent surface rupture results and likely significant errors in slip-at-depth estimates. Non-elastic effects in this sense may be caused by movements on subsidiary faults, folding of rock strata, change of shape of soft, deformable zones, and viscoelastic deformation of the ductile lower crust; these effects are witnessed most evidently by post-seismic movements, commonly observed in the days to months after large earthquakes, and also by aftershock earthquake events that are located off the main fault.Improving our understanding of these effects is important, as the relationships between fault slip and earthquake magnitude forms a significant component of seismic hazard analysis. In this specific case, improving our model of slip along all faults involved in the 2016 Kaikoura earthquake will enhance models of crustal stress accumulations in this region, key to developing improved short and medium term earthquake forecasts and seismic hazard analysis. Further, developing an improved insight of the mechanisms that pertain in accretionary prisms located above subduction interfaces is highly significant for understanding tsunami generation, both in New Zealand and elsewhere.We have an opportunity to take advantage of recent significant conceptual and processing developments in the field of 3-D strain modelling made at the Earth Observatory of Singapore (EOS), an Institute of Nanyang Technical University, Singapore. Combining geophysical and mathematical skills, the group headed by Asst. Prof. Sylvain Barbot has developed an approach to modelling complexity in crustal deformation that is significantly more computationally efficient than previous numerical approaches. This represents an unprecedented opportunity to take advantage of the very large and complex Kaikoura earthquake of 14th November 2016 to study in detail how accretionary wedges adjust their shapes as the position of tectonic plates, and the different components of the continental-ocean margin, evolve through time. The high quality data that we have collected as part of our on-going NERC urgency award (NE/P021425/1) makes this an attractive research collaboration for the EOS research team, while for us, it significantly extends the scope of our project, providing the opportunity to leverage our results to develop significant discoveries in the fundamental behaviour of fault movement, earthquake generation and landscape evolution. This will add significant value to the existing NERC-funded project, and form the basis for longer term research collaboration, whilst delivering important new information for seismic hazard analysis, helping to build resilience against natural hazards.