Remotely Triggered Slope Failures and Turbidity Currents on the Cascadia Margin

北美构造板块与胡安·德·富卡、戈尔达和探险家板块的汇合形成了卡斯卡迪亚俯冲带，从加利福尼亚北部延伸1100公里，一直延伸到太平洋西北部的加拿大温哥华岛。在构造板块交汇的海面上，形成了厚厚的楔形沉积物。由于陆地上的侵蚀和沉积物远离海岸线的运输，形成了沉积物楔，两块板块相互滑动造成的压缩使楔变厚。最近世界各地的大地震和海啸提高了人们对发生在卡斯卡迪亚边缘的过程所造成的自然灾害的认识。这些过程中有许多都与泥沙楔有关，特别是泥沙斜坡的破坏可能导致山体滑坡和产生局部海啸。该项目将有助于确定控制卡斯卡迪亚边缘沉积物楔上边坡破坏开始的过程。了解泥沙坡失的路径和触发因素是揭示过去地震历史和评估相关地震、海啸和海底滑坡危害的关键。该项目支持研究生和本科生的培养。从卡斯卡迪亚俯冲带海底地震仪部署的卡斯卡迪亚倡议项目返回的近期温度、压力和地震数据的初步检查表明，斜坡破坏和沉积物流动不仅可以由当地大地震触发，还可以由遥远地震的地震波触发，包括2012年苏门答腊岛海岸外的Mw8.6地震。如果这一解释得到本项目相关资料进一步处理和解释的证实，将对当前的几个科学问题产生重大影响，包括：(1)大逆冲地震重复周期的确定；(2)增生边缘楔形厚沉积物对地表地震震动的放大；(3)有机碳在沉积物碎屑流中的转移，这些碎屑流起源于浅大陆架，最终埋藏于深海平原，是全球碳循环的关键海洋组成部分。该项目的最终产品将是一个新的模型，用于识别Cascadia边缘可能容易发生边坡破坏的部分。

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.