- © 2009 by the Seismological Society of America
Geohazards monitoring can benefit greatly from the integration of seafloor and land observations, because many of the most seismogenic zones and active volcanoes are situated in oceanic basins (NRC 2000). Similarly, many volcanic and seismic areas located in coastal zones extend their activities into nearby marine sectors. The known features of these marine activities are restricted to episodic events, and nothing much is known about the long-term processes. However, marine technology has advanced over the past two decades to the point where long-term and permanent observatories and networks are under development on the seafloor. This has allowed investigations of geophysical processes at both global and regional scales in the Pacific Ocean and the European margin, under different programs from the United States, Canada, Japan, and the European Community (see Delaney et al. 2000; Stutzmann et al. 2001; Shirasaki et al. 2003; and Romanowicz et al. 2006; for a review, see also Favali and Beranzoli 2006). Japan was the first country to work on the extension of its geophysical monitoring to the ocean floor (Kasahara et al. 2006), and now has eight cabled seafloor observatories operating to date within the framework of the ARENA (Advanced Real-time Earth Monitoring Network in the Area) project. At the present feasibility study stage, ARENA is designed to deploy a mesh-like network of underwater cables that connects both terrestrial and underwater observatories all around the Japanese archipelago (Massion et al. 2004).
In the Pacific Ocean, the NEPTUNE5 project was jointly undertaken by the United States and Canada in the late 1990s and is among the most representative examples of state-of-the-art marine technology (http://www.neptune.washington.edu). NEPTUNE is a major component of the Dynamics of Earth and Ocean Systems (DEOS) initiative (http://neptunepower.apl.washington.edu/np_home.html) and the Ocean Observatories Initiative/Ocean Research Interactive Observatory Networks (OOI/ORION) program …