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Global Seismic Tomography

Final Report Summary - GST (Global Seismic Tomography)

Publishable summary

The funding of the Marie Curie (MC) Re-integration grant has been used very successfully to jumpstart an active research program in global seismic tomography. It has enabled us to finance a prototype of an underwater robot named 'Mermaid' that is able to record acoustic waves in the oceans at a depth of up to 2000 m while it floats freely with the deep ocean circulation at a speed of about 1-3 km/day, to develop electronics, algorithms, satellite communication and software needed to let the Mermaids operate independently, to continue a collaboration with mathematicians in the US and Belgium to define a new parameterisation of the Earth in terms of wavelets, and to finance participation of students and postdocs to international workshops and conferences directly related to these research activities.

This MC grant has been important in allowing the PI to submit proposals to the university of Nice for a BQR grant to finance the development of a Mermaid data acquisiton card, and to obtain a large European research council (ERC)-Advanced grant from the European community that has allowed us to go beyond the original, rather modest, goals of this MC project.

Towards the end of the four years of the MC grant the design of the Mermaid was finalised and we were able to order a flottilla of seventeen Mermaids using the ERC funding. A first large-scale tomography experiment with these instruments is planned for the Indian Ocean near the reunion hotspot in September 2012, and we are negotiating with INOCAR, the oceanographic institute of Equador to use their vessel for a deployment in the Pacific Ocean near the Galapagos hotspot.

We can do this because the tests with three Mermaid prototypes were very successful, apart from the loss of one prototype with an experimental hull of carbon fiber instead of aluminum. In particular, we have been able to record earthquakes at large distances and the ability to recognize even moderate earthquakes (down to magnitude 5.5) in the presence of ocean noise has exceeded our most optimistic expectations. We shall soon be able to open up the oceans – 2/3 of the earth's surface - for global seismic tomography, a fact that has nog gone unnoticed in the scientific press (e.g. Nature News, 7 Oct 2011 and NBC News, 18 Oct 2011). The drift of the Mermaids allows them to cover a large surface area over time, and to yield new information even for aftershocks coming from the same location.

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