Remotely Triggered Slope Failures and Turbidity Currents on the Cascadia Margin

北美构造板块与胡安·德·富卡、戈尔达和探险者板块的汇合形成了卡斯卡迪亚俯冲带，从加利福尼亚州北部延伸到太平洋西北部的加拿大温哥华岛，绵延1100公里。在构造板块交汇的近海，形成了一层厚厚的楔形沉积物。泥沙楔体是由于陆地侵蚀和泥沙运离海岸线而形成的，而由于两个板块相互滑动而产生的挤压使泥沙楔体变厚。最近世界各地的大地震和海啸提高了人们对卡斯卡迪亚边缘发生的过程造成的自然灾害的认识。这些过程中的许多都与沉积物楔体有关，特别是可能导致山体滑坡和局部海啸的沉积物斜坡的破坏。该项目将有助于确定控制卡斯卡迪亚边缘沉积楔形物上斜坡破坏开始的过程。了解泥沙边坡破坏的路径和触发因素是解开过去地震历史和评估与之相关的地震、海啸和海底滑坡灾害的关键。该项目支持研究生和本科生的培训。对卡斯卡迪亚俯冲带外海底地震仪布设的卡斯卡迪亚倡议方案返回的最近温度、压力和地震数据的初步检查表明，斜坡破坏和泥沙流动不仅可能由本地大地震触发，也可能由远距离地震的地震波触发，包括苏门答腊岛海岸外的2012年Mw8.6地震。如果这一解释得到本项目期间对相关数据的进一步处理和解释的证实，将对目前的几个科学问题产生重大影响，其中包括：(1)确定巨型逆冲地震的重复间隔，(2)增加边缘楔体中的厚沉积物对地表地震震动的放大，(3)沉积物泥石流中有机碳的转移，这些泥石流起源于浅层大陆架，最终埋藏在深海平原，这是全球碳循环的一个关键海洋组成部分。该项目的最终产品将是一种新的模型，以确定卡斯卡迪亚边缘可能容易发生斜坡破坏的部分。

Convergence of the North American tectonic plate with the Juan de Fuca, Gorda, and Explorer plates creates the Cascadia subduction zone, extending 1100 km from northern California to Canada's Vancouver Island in the Pacific Northwest. Offshore where the tectonic plates meet, a thick wedge of sediment develops. The sediment wedge forms as a result of erosion on land and transport of the sediment away from the coastline, and the wedge is thickened by the compression resulting from the two plates sliding by each other. Recent great earthquakes and tsunamis around the world have heightened the awareness of the natural hazards posed by the processes occurring along the Cascadia margin. Many of these processes are linked to the sediment wedge, particularly the failure of sediment slopes that may lead to landslides and generate local tsunamis. This project will help to identify the processes controlling the initiation of slope failure on the sediment wedge at the Cascadia margin. Understanding the paths and triggers for sediment slope failures is key to unraveling the history of past earthquakes and assessing the associated earthquake, tsunami, and submarine landslide hazards. The project supports the training of graduate and undergraduate students.Preliminary examination of recent temperature, pressure and seismic data returned from the Cascadia Initiative program of Ocean Bottom Seismometer deployments off of the Cascadia subduction zone has shown that slope failures and sediment flows can be triggered not only by local great earthquakes, but also by the seismic waves from distant earthquakes, including the 2012 Mw8.6 event off the coast of Sumatra. If this interpretation is substantiated by further processing and interpretation of the related data during this project, it will have a major impact on several current scientific issues, including (1) identification of megathrust earthquake recurrence intervals, (2) the amplification of surface seismic shaking by the thick sediments in the accretionary margin wedge, and (3) the transfer of organic carbon within sediment debris flows that originate on the shallow continental shelf and end with burial in the abyssal plain, a key marine component of the global carbon cycle. The end product of the project will be a new model to identify sections of the Cascadia margin that may be prone to slope failures.