Noisy Oceans

Non-seismic events (NSE) include all seismic events non-associated with tectonic movements along a fault or active seismic sources. A vast variety of different signals are routinely recorded at sea, for example, gas migration within the shallow sediments and gas emission from the seafloor in hydrothermal vents, pockmarks and mud volcanoes; volcanic tremors; tides and other ambient noise; anthropogenic noise; military tracking and marine mammal calls. The waveforms of these signals are recognizably different from earthquakes but the lack of a waveform database for the classification of non-tectonic seismic events makes it challenging to detect and study these events. Monitoring Seismic and Acoustic Waves at Sea describes the non-tectonic related seismic signals, show examples of their waveforms, discuss the methodologies allowing to detect and study them, outline their impact and the remaining questions and establish a nomenclature for scientists working on these events, to ease future communications. Studies show examples where NSE's are used for gaining new knowledge in multiple domains of sciences. Volcanic tremors are studied to track the magma movements and used as a successful early warning system to mitigate the volcanic hazard for years. Whale calls recorded on seismic stations are used to track whales and study their habit changes connected to environmental changes. Ambient seismic noise is used to infer the seafloor physical properties. Monochromatic short duration events are suggested to be the expression of fluid migration within the shallow sediments, and they are used for the quantification of local seafloor Methane emission. Case studies show that NSE's allow gaining knowledge in processes involved in climate change. Also, they are used for geo-hazard mitigation. They, therefore, have a huge economic and societal importance. Volume highlights include: - Summary of known unconventional non-tectonic related seismic signals at sea - Methodological approaches to detect and distinguish between tectonic (earthquake, tsunamis) and non-tectonic (landslides, glaciation) seismic signals at sea - Geophysical signals mostly studied by marine seismologic techniques combined with other marine geoscience techniques - Useful contributions for marine seismologists, acousticians, geologists, ecologists, geochemists and biologists - Beneficial for industry and the military professionals discussing the monitoring methodologies exploiting these signals - Case studies from specialists of each type of geophysical signals at various depths in sea