Earthquakes and Imaging beneath the Oceans using Submarine Telecoms Cables as Seismometers

今天，虽然地球表面70%是水，但几乎所有的地震传感器都在陆地上，因为在海底安装有线传感器太困难了，而且成本高得令人望而却步。这大大限制了我们确定水下地震事件的震源机制以及我们对海洋下地球内部结构和过程的了解的能力。然而，大洋岩石圈驱动着许多板块构造，洋壳储存和回收碳和许多宝贵的资源，因此了解地球上这些巨大的区域是重要的。2018年，英国国家物理实验室和国际同事证明，现有的电信光缆(用于互联网流量)可以用作地震(地震)波探测器，当应用超精密干涉激光技术对其进行讯问时。这项革命性的技术为一种令人振奋的新可能性铺平了道路：在大多数海洋和大洋底部已经存在的电信电缆基础设施的基础上，实施全球水下地震监测网络。这项研究将侧重于对通过世界上第一次地面和海底电缆实验获得的地震数据进行建模和新的分析。与记录某一点上的地球运动的地震仪不同，这些电缆记录的是沿电缆的各种可控距离的平均运动。这为创新思维带来了令人兴奋的建模挑战和机遇。研究问题1.在海底通信电缆上记录地震记录的精确度有多高？2.这些记录与常规地震仪记录有何不同？3.这些记录对地震探测和地球成像有什么新的利基？4.我们在地下能看到以前看不到的什么？-探索！方法这个项目将专注于数值模拟和分析来自野外实验的实验数据。该研究将侧重于地震探测和利用地震波对地球成像，但将扩展到环境噪声、微震的监测以及海洋和固体地球中较长期过程的监测，具体取决于学生的兴趣。为了解决研究问题，将进行一系列任务：1.学生将研究地震波与光缆相互作用产生的信号并建立模型。学生将能够通过与在陆地和水下使用光缆现场获取的实际数据进行比较来验证模型。2.学生将有机会参加这些现场实验，并将学习现代激光、光学物理和光学传感器的发展。3.从一组地面和海底电缆的实验数据开始，学生将在浅水和深海建立预期的基于光纤的海洋距离探测机制的模型，评估基于海底电缆的全球地震网络的可行性。4.从地震中获得的数据将用于描述地震的特征和对地球内部进行成像。培训将提供全面的培训方案，既包括专业科学培训，也包括通用可转让和专业技能。这将包括演示和编程技能、科学写作、网络和专业安置。你将接受地震学领域相关学科的培训，以及使用地震数据有效询问地球内部所需的建模、分析和成像方法。

Today, whilst 70% of the Earth's surface is water, almost all seismic sensors are on land because it is too difficult and prohibitively expensive to install cabled sensors on the sea floor. This substantially limits our ability to identify the source mechanisms of underwater seismic events and our understanding of the internal structure and processes in the Earth beneath oceans. Yet oceanic lithosphere drives much plate tectonics, and oceanic crust stores and recycles carbon and many valuable resources, so understanding these huge areas of our planet is important.In 2018, the UK National Physical Laboratory and international colleagues, demonstrated that existing telecommunication optical fibre cables (used for Internet traffic) can be used as seismic (earthquake) wave detectors when ultra-precise interferometric laser techniques are applied to interrogate them. This revolutionary technique paves the way to an exciting new possibility: the implementation of a global monitoring network for underwater earthquakes based on the telecommunications cable infrastructure that already lies on the bottom of most seas and oceans. This research will focus on modelling and novel analysis of seismic data acquired with world-first experiments on terrestrial and submarine cables. In contrast with seismometers which record earth motion at a point, these cables record motion averaged over various controllable distances along the cable. This poses exciting modelling challenges and opportunities for innovative thinking. Research questions1. With what accuracy can seismograms be recorded on submarine telecoms cables?2. How do these recordings differ from recordings made on regular seismometers?3. What novel niche do the recordings open for earthquake detection and imaging of the Earth?4. What can we see in the subsurface that we could not see previously? - Explore!MethodologyThis project will focus upon numerical modelling and analysis of experimental data from field experiments. The research will focus on earthquake detection, and the use of seismic waves for imaging the Earth, but will extend to the monitoring of environmental noise, microseisms and the monitoring of longer terms processes in the oceans and solid Earth, depending on the interests of the student. To address the research questions a series of tasks will be undertaken:1. The student will study and model the signals resulting from the interaction between seismic waves and optical fibre cables. The student will be able to validate the model by comparison with actual data acquired in the field with optical fibre cables on land and underwater. 2. The student will have the opportunity to participate in these field experiments, and will learn about modern lasers, optical physics and the development of optical sensors. 3. Starting from experimental data from a set of terrestrial and submarine cables, the student will model the expected fibre-based detection mechanism across oceanic distances, in both shallow and deep waters, assessing the feasibility of a global seismic network based on submarine cables. 4. Data acquired from earthquakes will be used to characterise the earthquakes and to image the Earth's interior. TrainingA comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. This will include presentation and programming skills, scientific writing, networking, and a professional placement. You will be trained in the relevant disciplines which underlie the field of seismology, along with the required modelling, analysis and imaging methods necessary to use the seismic data for effective interrogation of the Earth's interior.