The RHUM-RUM project (Réunion Hotspot and Upper Mantle – Réunions Unterer Mantel, www.rhum-rum.net) allowed to deploy 57 three-components, broad-band Ocean Bottom Seismometer (OBS) on the ocean floor around La Réunion from Nov. 2012 to Dec. 2013. Interestingly, part of the network was located beneath a route of heavy ship traffic connecting SE-Asia and the South-Atlantic region. By combining the trajectories of passing ships - provided by AIS (Automatic Identification system) GPS data - with our geophysical data recorded on the ocean floor, we show that both hydro-acoustic and seismic spectral analyses exhibit clear signals associated to vessels in the high frequency range of our seismic data (between 1 and 50 Hz). Large cargo vessels are detected several hours before and after their closest point of approach and show clear Doppler effects.
The goals of this Phd are the following :
- Develop a method based on polarization analysis to estimate the orientation and the distance of a ship from a single OBS. Make it work even if several ships pass by at the same time. Automatize the process.
- Use this method to retrieve the true OBS orientation with a good accuracy as they lose north when the they are sunk in the ocean.
- Code an algorithm capable of recognizing a ship from his acoustic signature allowing to follow it through a network of OBS even if we lose the acoustic contact at some period.
- Transpose those methods to other noise source in the ocean.