S14A-01 INVITED 17:00h
Gutenberg Lecture: Bridging the gap Between Seismology and Oceanography: New Phenomena in the Background Seismic Wavefield
It has long been known (e.g. Longuet-Higgins, 1950) that the source of the microseismic noise peak, which pervades seismic records in the period range 1-10 sec, is generated by complex non-linear interactions between ocean waves and the seafloor. A less obvious signal, discovered six years ago by Japanese scientists deep in the longer period noise of land-based seismic stations ($>150$ sec), is that of Earth's continually excited free oscillations. This "hum" now appears to also be generated through a non-linear coupling mechanism involving the atmosphere (winds), the ocean (infragravity waves) and the solid earth. The realization that a large portion of the earth's seismic noise, over a wide frequency band, is made of Rayleigh waves has opened up new horizons for the study of earth's crust and upper mantle 3D structure, as well as other non-tectonic phenomena such as the motions of glaciers. I will also argue that the deployment of arrays of ocean observatories comprising sensors recording motions from the seafloor through the entire water column is a necessary next step, complementing land and space-based observations, to further our understanding of this wide class of intriguing atmosphere/ocean/solid earth interactions.