Collaborative Research: Illuminating the Cascadia plate boundary zone and accretionary wedge with a regional-scale ultra-long offset multi-channel seismic study

合作研究：通过区域尺度超长偏移多道地震研究阐明卡斯卡迪亚板块边界带和增生楔

• 批准号: 1827452
• 负责人: Suzanne Carbotte
• 金额: $ 74.96万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-11-01 至 2022-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1827452&HistoricalAwards=false
• 关键词: Collaborative; Research; Illuminating; Cascadia; plate

At the Cascadia Subduction Zone, the slow ongoing descent of the Juan de Fuca plate beneath the northwestern coast of North America has generated large earthquakes and associated tsunami in the past. Geologic records suggest that some sections of the subduction zone fault or "megathrust", which extends ~35-90 miles seaward from the coasts of northern California all the way to southern British Columbia, slipped less than other sections during the last large earthquake (1700 AD), and that in some prior EQ only parts of the subduction zone ruptured. Whether these along-margin variations may persist in future EQ has important implications for quantifying earthquake and tsunami hazards within the heavily populated Pacific Northwest margin. Geologic structure such as seamounts and other topographic features in the descending Juan de Fuca plate, the structure and properties of the thick folded and faulted package of sediments that forms above the subduction zone fault, or the properties of megathrust fault rocks, could contribute to these along-margin variations. However the current observations are limited and allow for a wide range of possible future earthquake scenarios. Modern marine seismic reflection imaging techniques provide the best tools available for illuminating a subduction zone to the depths of the earthquake source region and below. The overall goal of this project is to acquire a regional grid of modern marine seismic reflection data spanning the entire Cascadia Subduction zone to image how the geologic structure and properties of this subduction zone vary both along and across the margin. This project will serve the national interest in that the acquired data will form a foundational dataset for future initiatives focused on hazard assessment in the U.S. Pacific Northwest, including for an earthquake early warning network and deep drilling to sample the fault zone rocks, and it will promote the advancement of science by providing a new regional framework relevant for the wide range of multi-disciplinary onshore and offshore studies conducted in this region over the past several decades.Specifically, this study will use ultra-long-offset multi-channel seismic (MCS) data to characterize subducting plate and accretionary wedge structure, and properties of the megathrust, to address the following specific questions: 1. Are there any systematics in the structure and properties of the incoming Juan de Fuca plate, the megathrust zone, and accretionary wedge associated with inferred paleo-rupture segmentation? 2. Are there down-dip variations in megathrust geometry and reflectivity indicative of transitions in fault properties, and what are the properties of the potentially tsunamigenic shallow portion of the megathrust? Long 15-km-offset MCS data will be acquired along twenty 2-D profiles at 50-100 km spacing oriented perpendicular to the margin and located to provide coverage in areas inferred to be paleo-rupture patches and their boundary zones. The survey will also include one continuous strike line along the continental shelf centered roughly over gravity-inferred fore-arc basins to investigate possible segmentation near the down-dip limit of the seismogenic zone. The margin normal lines will extend approximately 50 km seaward of the deformation front to image the region of subduction bend faulting in the incoming oceanic plate, and landward of the deformation front to as close to the shoreline as can be safely maneuvered. The acquired data will be designed to characterize 1) the deformation and topography of the incoming plate, 2) the depth, topography and reflectivity of the megathrust, 3) sediment properties and amount of sediment subduction, 4) the structure and evolution of the accretionary wedge, including geometry and reflectivity of fault networks, and how these properties vary along strike, spanning the full length of the margin and down dip across what may be the full width of the seismogenic zone at Cascadia. The data will be processed to pre-stack depth migration using state-of-the art seismic processing techniques and will be made openly available to the community, providing a high-quality data set illuminating the regional subsurface architecture all along the Cascadia Subduction Zone.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在卡斯卡迪亚俯冲带上，过去在北美西北海岸下方的胡安·德福卡板的下降缓慢，过去造成了大地震和相关的海啸。地质记录表明，俯冲带断层或“巨型震荡”的某些部分延伸到距北加利福尼亚沿岸的35-90英里，一直到不列颠哥伦比亚省南部，在最后一个大地震（1700 AD）中，其较小的部分比其他部门少于其他部门，而在某些eq仅在eq的部分中，分子损坏了。这些沿线变化是否可能会持续在未来的EQ中，这对于量化人口稠密的西北边缘内的地震和海啸危害具有重要意义。地质结构（例如海底和其他地形特征）在下降的胡安de Fuca板上，厚折叠和故障的沉积物包装的结构和特性，这些沉积物的结构和特性形成了俯冲区域上方，或者可能会导致这些沿着这些量的质量变化。但是，当前的观察结果是有限的，并允许多种可能的未来地震场景。现代海洋地震反射成像技术提供了可用的最佳工具，用于照亮地震源区域及以下深处的俯冲带。该项目的总体目标是获取跨越整个卡斯卡迪亚俯冲带的现代海洋地震反射数据的区域网格，以图像该俯冲区的地质结构和特性如何在整个边缘沿途和跨越跨越。该项目将有助于国家的利益，即获得的数据将构成一个基础数据集，以供未来的举措，重点介绍美国太平洋西北地区的危险评估，包括用于地震早期警告网络和对故障区域的深入钻井，这将通过提供与多个越野范围的越野范围的跨越范围的越野范围的跨越范围的越野范围的越野范围，以促进科学的进步，并促进了越野范围的越野范围。具体来说，本研究将使用超长的多通道地震（MCS）数据来表征俯冲板和增生的楔形结构和大型质量的特性，以解决以下具体问题，以解决以下具体问题：1。是否有任何与不断增长的fucate de fuca de fuca de fucate decultions the Megath the Megathrive decuttion the Megathrive decultions the Megathrive dectription和coptriptions negrent的系统的系统。细分？ 2。大型几何形状和反射率的垂直变化指示断层特性中的过渡，以及巨型巨像的潜在tsunamigenic浅层部分的特性是什么？长达15公里的MCS数据将在50-100 km间距垂直于边缘的50-100 km间距沿二十d-d轮廓获取，并位于延伸的范围内，并在推断为古爆裂斑块及其边界区域中提供覆盖范围。该调查还将包括一条连续的罢工线，沿着大约以重力提交的前弧盆地为中心的大陆架子，以研究地震生成区的下倾极限附近的可能分割。边缘正常线将延伸大约50 km的变形正面海向海向海洋，以形象成像进入的海洋板中俯冲弯曲断层的区域，而变形前的陆上是可以安全地操纵的靠近海岸线。 获得的数据将设计为表征1）传入板的变形和地形，2）大型象征的深度，深度，地形和反射率，3）沉积物性能和沉积物俯冲的数量，4）4）增值楔的结构和进化，包括这些物体的几何形状以及跨度的范围，以及整个层面的范围，以及整个范围的范围，整个范围的范围是整个范围的范围。卡斯卡迪亚地震源区的宽度。 The data will be processed to pre-stack depth migration using state-of-the art seismic processing techniques and will be made openly available to the community, providing a high-quality data set illuminating the regional subsurface architecture all along the Cascadia Subduction Zone.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.