Probabilistic cable damage risk assessment method for seafloor cabled observatory and its application to hydrothermal fields

As part of a recent Japanese governmental project, the government has planned and begun a program to develop a seafloor cabled observatory that facilitates the long-term monitoring of hydrothermal vents and the ecological changes surrounding them. Because commercial cables are typically laid to avoid rough terrain and hydrothermal fields, there is no established method to assess system damage risk for a cabled observatory installed on a hydrothermal field. In this article, we propose a probabilistic cable damage risk assessment method for a seafloor cabled observatory installed on a hydrothermal field. The core concept of our method is the use of probability functions to estimate the system damage risk for the system of a seafloor cabled observatory laid on a defined route. The considered damage factors are potential heat damage risks to the cabled system and damage risks caused by frequent contact between the cable and seafloor. The product of each risk probability represents the total survivability of the system on the route. The proposed method was applied to the Oomuro-hole hydrothermal field on the active submarine Oomuro-dashi volcano, where remotely operated vehicle (ROV) surveys have been performed. The discovered risk factors are organized into a geographic database, and risk value fields are generated. We planned and evaluated several candidate routes that connect a target site for observation to the cabled system terminal unit. Finally, the proposed method derives quantitative system survivability values for the candidate routes and facilitates planning of the layout for a seafloor cabled observatory installed on a hydrothermal field. © 2018, Marine Technology Society Inc. All rights reserved.