Physics and Astronomy Colloquium
Twenty Thousand Leagues Under the Sea with a Fleet of Seismic Robots
Presented by Frederik J Simons, Princeton
In the last few decades, seismologists have mapped the Earth's interior (crust, mantle, and core) in ever increasing detail. Natural earthquakes, the sources of energy used to probe the Earth's inside via seismic computerized tomography, occur mostly on tectonic plate boundaries. Seismometers, the receivers of earthquake wave motion, are located mostly on dry land. Such fundamentally inadequate 'source-receiver' coverage leaves large volumes inside the Earth entirely unexplored. Here be dragons! Placing seismic stations on the ocean bottom is among the solutions practiced successfully today. But there are exciting alternatives. Enter MERMAID: a fully autonomous marine instrument that travels deep below the ocean surface, recording global seismic activity - and marine environmental data - and reporting it by surfacing for satellite data transmission. I will discuss a century of Earth imaging, a decade of instrument design and development, and a day in the life of exploring the challenging - and wet - places that our scientific journey has taken us in our study of mantle plumes below the Galapagos Islands, and underneath French Polynesia, as part of an international academic consortium, EarthScope-Oceans. I will furthermore discuss how, beyond earthquakes, MERMAID hears the sounds of ocean waves that generate microseisms of the Rayleigh variety, I will make a brief detour to explain how the up-down heave of the ocean manages to excite even Love waves in the solid Earth... and I will show MERMAID's unprecendent set of hydroacoustic records of the Hunga-Tonga eruption, the volcanic explosion heard around the world.
Refreshments will not be available at this event.
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