First remote sensing of turbidity currents via seismic signals: how much can we learn about the longest sediment flows on Earth?

浊流在全球范围内将大量沉积物和有机碳输送到深海，并对海底基础设施构成相当大的危险。尽管技术取得了进步，但众所周知，浊流很难监测，因为它们的位置相对较难到达，而且往往无法预测发生的情况。最重要的是，它们的强大性质往往会损坏放置在它们路径上的工具。过去5年的开创性工作表明，使用系泊设备监测浑浊水流是可能的。最近，其中包括2020年1月从刚果河河口流出1200公里的泥石流；这是地球上迄今测量到的(任何类型的)最长泥石流。然而，系泊测量是昂贵的，而且在后勤上也很困难。此外，它们位于浑浊洋流中，因此处于危险之中。这些挑战意味着，只有几个现场可以研究，但我们需要研究世界各地的浑浊流，以了解它们的控制。因此，我们需要浑浊水流的传感系统，而浑浊水流的位置是远离危害的。令人兴奋的是，最近从西非刚果峡谷近海获得的海底地震仪(OBS)数据表明，浑浊洋流发出独特的地震信号。这些新识别的地震信号现在可以通过位于事件外部的遥感系统来监测大范围的事件。为了改变对浊流及其更广泛影响的理解，我建议开发全球适用的方法，使用刚果峡谷的OBS数据远程监测浊流，已知刚果峡谷存在强烈的浑浊流。为了做到这一点，OBS的结果将与相邻系泊地点提供的关于水流及其时间的独立信息进行比较。这将有助于了解地震信号不仅能告诉我们浑浊流何时发生，而且还能告诉我们内部流动结构及其演变甚至侵蚀速率。OBS调查很有可能成为未来海底危险监测的重要支柱。该项目的结果将成为今后此类调查分析的基础。

Turbidity currents transport globally significant volumes of sediment and organic carbon into the deep-sea and pose a considerable hazard to sea floor infrastructure. Despite advances in technology, turbidity currents are notoriously difficult to monitor due to their relatively inaccessible location and often unpredictable occurrence. Most importantly, their powerful nature often damages instruments placed in their path. Pioneering work in the last 5 years has shown it was possible to monitor turbidity currents using moorings. Most recently, this included a flow that ran out for >1,200 km from the Congo River mouth in Jan. 2020; the longest sediment flow (of any type) yet measured on Earth. Mooring measurements, however, are expensive and logistically difficult. In addition, they are located within turbidity currents, and thus in harm’s way. These challenges mean that only a few field sites can ever be studied, yet we need to study turbidity currents at locations worldwide to understand their controls. We therefore need sensing systems for turbidity currents, which are located out of harm’s way. Excitingly, recently acquired ocean bottom seismometer (OBS) data from the Congo Canyon offshore West Africa suggest that turbidity currents emit distinctive seismic signals. These newly-recognised seismic signals now enable monitoring events across large areas via remote sensing systems located outside the event. To make a step change in understanding turbidity currents and their wider impacts, I propose to develop globally applicable methods to remotely monitor turbidity currents using OBS data from the Congo Canyon, where powerful turbidity currents are known to occur. To do this, the OBS results will be compared to independent information provided by adjacent moorings on the flows and their timing. This will help to understand what seismic signals can tell us about not only when turbidity currents occur, but also the internal flow structure and its evolution and even erosion rates. OBS surveys have a high potential of constituting an important pillar of sea floor hazard monitoring in the future. The results of this project will form the basis of the analyses of such future surveys.