Marine instrumentation for geophysical investigations: From electromagnetic to hydroacoustic, toward permanent observatories

We present some of the latest developments in marine instrumentation for geophysical instrumentation, and their evolutions. For several years, we have been developing magnetotelluric seafloor instruments. Initially for deep mantle studies, recording at low frequency with long term instruments, more recently for crustal studies and industrial exploration with high frequency recording. We are also currently developing seafloor electromagnetic observatories. Thanks to collaborations with the Pacific Marine Environmental Laboratory (NOAA & Oregon State University) in Newport, Oregon (USA) and with the acquired knowledge at their contact we are also developing autonomous hydrophones to monitor seismicity of oceanic areas and the population of marine mammals. All these geophysical investigation and technical developments are leading us toward the development of permanent geophysical observatories.