Recently, a number of novel bacteria have been isolated from a mud sample taken in the Challenger Deep of the Mariana Trench. Although the need exists for taking sediment samples at full ocean depth, no high-power remotely operated vehicle (ROV) with full depth capability
and the ability to take sediment samples existed anywhere in the world as of April 2005. JAMSTEC started developing such a sediment sampling system beginning in April 2005. The system consists of a sampling launcher and a pre-observation probe vehicle. The launcher contains a water sampler
as well as sediment samplers. It launches the probe vehicle to make a preliminary survey, dropping the sediment sampler to obtain a sample. We carried out four sea trials from January 2007 to June 2008, including dives in the Mariana Trench, and we were able to obtain sediment samples from
the deepest part of the Challenger Deep.
We have developed a new system for real-time observation of tsunamis and crustal deformation using a seafloor pressure sensor, an array of seafloor transponders and a Precise Point Positioning (PPP ) system on a buoy. The seafloor pressure sensor and the PPP system detect tsunamis, and the pressure sensor and the transponder array measure crustal deformation. The system is designed to be capable of detecting tsunami and vertical crustal deformation of ±8 m with a resolution of less than 5 mm. A noteworthy innovation in our system is its resistance to disturbance by strong ocean currents. Seismogenic zones near Japan lie in areas of strong currents like the Kuroshio, which reaches speeds of approximately 5.5 kt (2.8 m/s) around the Nankai Trough. Our techniques include slack mooring and new acoustic transmission methods using double pulses for sending tsunami data. The slack ratio can be specified for the environment of the deployment location. We can adjust slack ratios, rope lengths, anchor weights and buoy sizes to control the ability of the buoy system to maintain freeboard. The measured pressure data is converted to time difference of a double pulse and this simple method is effective to save battery to transmit data. The time difference of the double pulse has error due to move of the buoy and fluctuation of the seawater environment. We set a wire-end station 1,000 m beneath the buoy to minimize the error. The crustal deformation data is measured by acoustic ranging between the buoy and six transponders on the seafloor. All pressure and crustal deformation data are sent to land station in real-time using iridium communication.
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