Illuminating northern Cascadia earthquake faulting using satellite and airborne geodesy

地震断层有助于塑造我们的星球，控制关键自然资源的分布，并影响我们的气候。地震也是最重大的全球自然灾害之一，本世纪预计将有数百万人死亡，加拿大大部分地区面临破坏性震动和海啸的风险。因此，了解是什么决定了地震的位置、大小和时间，是地球物理学面临的重大挑战之一。 2017年1月，我搬到维多利亚大学，试图通过建立一个主要专注于卡斯卡迪亚北部构造的新研究小组来应对这一挑战。这笔探索基金--连同支持相关基础设施需求的加拿大创新基金会提案--将资助两个截然不同的项目，概述如下。这两种元素都利用了新一波的卫星和机载传感器，这些传感器正在彻底改变我们绘制与地震断层相关的地表形变和地形的能力。进一步的动力来自最近全球巨型逆冲地震的激增，这些地震撕毁了俯冲带行为的规则手册。 A部分：InSAR绘制卡斯卡迪亚表面形变图 我们将使用新一波干涉合成孔径雷达(InSAR)卫星来产生第一次空间连续的地表形变测量，跨越整个卡卡迪亚前弧。与目前用于变形监测的稀疏全球定位系统(GPS)站相比，InSAR可以极大地改善空间复盖范围并提高对垂直位移的敏感度。一个关键目标是绘制巨型逆冲的锁定和稳定滑动模式，以便限制(未来)地震滑动的可能向下极限，并确定沿俯冲带走向的任何变化。第二个目标是探测与地壳浅层断层、岩浆作用和滑坡有关的上板块变形。 B部分：机载激光雷达测绘上盘断层 GPS测量表明俯冲带向陆地的永久性缩短，但负责的上板块断层在很大程度上是未知的。过去浅层地震的迹象包含在地形中，但由于植被茂密，传统的摄影遥感无法获取。通过利用现有的激光雷达持有量，并从无人机平台收集我们自己的新数据，我们将第一次在森林覆盖下进行窥视。我们的目标是绘制上板块断层图，通过随后的古地震工作确定它们的意义和滑动速率，并确定它们在弧前变形运动学中的作用。 通过与附近太平洋地球科学中心的NRCan科学家在这两个项目上合作，我们将确保成果转化为切实的社会效益，例如改善地震监测能力和概率地震危险评估。

Earthquake faulting helps shape our planet, controls the distribution of key natural resources, and impacts our climate. Earthquakes are also amongst the most significant global natural hazards, with millions of fatalities forecast this century and large parts of Canada at risk from damaging shaking and tsunami. Understanding what governs the location, size, and timing of earthquakes is therefore one of the grand challenges of geophysics. In moving to the University of Victoria in January 2017, I seek to tackle this challenge by building a new research group focused primarily on the tectonics of northern Cascadia. This Discovery Grant - together with a Canadian Foundation for Innovation proposal which supports related infrastructural needs - will fund two distinct projects, outlined below. Both elements exploit a new wave of satellite and airborne sensors which are revolutionizing our ability to map surface deformation and topography associated with earthquake faulting. Further motivation is provided by a recent global surge of megathrust earthquakes which have torn up the rule book on subduction zone behaviour. Part A: Mapping Cascadia surface deformation with InSAR We will use a new wave of Interferometric Synthetic Aperture Radar (InSAR) satellites to produce the first spatially-continuous surface deformation measurements that span the entire Cascadia fore-arc. InSAR can provide vastly-improved spatial coverage and enhanced sensitivity to vertical displacements compared to the sparse Global Positioning System (GPS) stations currently used for deformation monitoring. A key objective is to map patterns of locking and stable slipping of the megathrust, in order to constrain the likely down-dip limit of (future) seismic slip and identify any variations along the strike of the subduction zone. A secondary goal is to detect upper plate deformation associated with shallow crustal faults, magmatism, and landsliding. Part B: Mapping upper plate faulting with airborne lidar GPS measurements imply permanent shortening landward of the subduction zone, but the responsible upper plate faults are largely unknown. Signatures of past shallow earthquakes are contained within the topography, but are inaccessible to traditional photographic remote sensing due to dense vegetation. By leveraging existing lidar holdings and collecting our own new data from an unmanned aerial vehicle platform, we will peer beneath the forested cover for the first time. Our aims are to map upper plate faults, determine their sense and rate of slip through ensuing paleoseismic work, and establish their role in fore-arc deformation kinematics. By collaborating with NRCan scientists at the nearby Pacific Geoscience Centre on both projects, we will ensure that results are translated into tangible societal benefits such as improvements to seismic monitoring capabilities and probabilistic seismic hazard assessments.