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

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 questions
1. 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!
Methodology
This 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.

Training
A 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.