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Monitoring the high-seas marine environment using passive hydroacoustic observatories


IPGP - Îlot Cuvier


Séminaires Géosciences Marines

Salle 310

Jean-Yves ROYER

IUEM, Brest

Since the Ocean is an excellent sound waveguide, passive acoustics proved to be one of the most performing tools for monitoring the high-sea marine environment over long-term periods and large areas. Passive acoustic monitoring is performed through long-term deployments of autonomous hydrophone arrays and provides insights on the low-frequency noise generated by natural, biologic and anthropogenic activities. Most of the plate boundaries being under sea, most of the world seismic and volcanic activity occurs in the oceans. However, due to the rapid attenuation of seismic waves in the solid Earth, the low-level seismic activity, for instance associated with seafloor spreading ridges, is not captured by land-based seismological networks, however it significantly contributes to the ocean acoustic noise level. This low-frequency noise (10-40 Hz) thus provides valuable information about the dynamics of active plate boundaries. This talk will present results from long-term monitoring of seafloor spreading ridges in the Atlantic and Indian oceans, with contrasted spreading rates from the ultra-slow Southwest Indian Ridge, the slow Atlantic and Central Indian ridges to the intermediate spreading Southeast Indian Ridge. Forward modeling of acoustic waves generated by earthquakes (T-waves) provide insights about the processes that produce them and the information carried by T-waves.