10 year video observation on deep seafloor at cold seepage site in Sagami Bay, central Japan

Abstract

As a part of multidisciplinary real-time observation at cold seepage site on deep seafloor which faces swarm earthquake area at a depth of 1175 m off Hatsushima Island in Sagami Bay, central Japan, video monitoring has been carried out for about 10 years by a cabled observatory. Through the observation, outbreak event such as mudflows caused by earthquakes, spawning of clams and other biological events were observed along with long-term phenomena such as sedimentation on seafloor associated with mudflow or the fluctuation of the amount of suspended particles. Some of these video images provide important information on the fluctuation observed by other sensors of the observatory, such as sub-bottom temperature and intensity of gamma-ray, indicating that those fluctuations were primarily related to such environmental changes on seafloor as sedimentation. On the other hand, extracting meaningful events or phenomena from a huge amount of stored video images needs tremendous time and effort. Effective methodology of scene detection and indexing is necessary