Contents I. Introduction
Since the mid-1990s, scientists hoped to observe the ocean from the seafloor which supported real-time, longterm and continuous observation. Seafloor observatories now have been acknowledged as the third observation platform for earth system after ground/sea surface and remote sensing [1]. In 1978, a number of seismographs connected by cable were laid by the Japan Meteorological Agency to monitor seismicity, which can be recognized as the prototype of seafloor observatories [2]. In recent decades, many countries have developed their own seafloor observation systems. Especially the Neptune Canada, the first regional seafloor observatory in the world [3] was successfully established in December, 2009 [4]. And the OOI (Ocean Observatories Initiative) conducted by USA is a networked infrastructure of science-driven sensor systems that measure the physical, chemical, geological, and biological variables in the ocean and seafloor on coastal, regional, and global scales [5].
