Offshore of the Hatsushima area, western Sagami Bay, are distributed along the submarine escarpment of eastern rim. Many geological, geophysical, and biological studies have been conducted at this cold seep still present. In May 2005 and January 2006, seismic reflection surveys were carried out in the Sagami Bay by R/V Kaiyo of JAMSTEC. In this paper, we identified the submarine structure of offshore Hatsushima around the chemosynthetic biocommunity area obtained by seismic survey results. These surveys provided very clear seismic images down to 1.5 seconds beneath the seafloor in two-way travel time. We identified three sedimentary units compared with the Ashigara Group and acoustic basement as the Shirahama Group (∼2 Ma) that is commonly absorbed in seismic images of the western Sagami Trough. We identified two reflectors of reverse polarity indicating fluid and/or gas existence of Horizons A and B in the trough-fill sediment layer. Deformed structures due to uplift of Izu Peninsula side are identified in trough-fill sediment layer zone near the submarine escarpment. These structures suggest the existence of concealed fault system or magma intrusion in the deep part of basement layer. In addition, wipe-out structures are recognized in the trough-fill sediment layer. These wipe-out structures are also related to the reflector of reverse polarity (Horizon A) in the trough-fill sediment layer, it was concluded that these structures were the fluid and/or gas based diapirs. The results of this study clarified the relationship between the geologic structures, the fluid and/or gas based diapirs and the high heat flow value area.

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  We review previous numerical simulations of interaction between fault segments on a plate interface based on a friction law, comparing combined events with single events on the amount of coseismic and preseismic slip. We find out the characteristics of combined event: (i) In case of multiple fault segments nearby enough to have short delay time of rupturing, coseismic slip is increased nearly in proportion to the size of combined fault segment while preseismic slip is almost the same as single event. (ii) In case of those distant enough to have long delay time of rupturing, seismic moment magnitude is almost the same as single event while preseismic slip is significantly increased by several tens percents. We discuss several combined earthquakes in Sumatra with short-term and long-term delay times and the possibility of megathrust earthquakes following the 2011 off the Pacific Coast of Tohoku Earthquake occurring off Kanto and off Sanriku with long-term delay time in the near future. We point out that seafloor observation of crustal deformation and seismicity off Kanto, Sanriku and Tokachi is necessary to enhance the detection ability of preseismic changes.

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  Scientific data visualization to convert simulation or observational data into images is one effective technique to intuitively understand the scientific features and meanings included in such data. This paper reviews the current status of research into largescale data visualization, including time-varying visualization, remote visualization, visualization using leading edge environments and optimization of the processes in a visualization pipeline. Visualization of a massive dataset produced by a large-scale numerical simulation takes a great deal of time and is not easy to perform on a single computer. Typical approaches to efficiently visualize such datasets are the parallelization of each process in the visualization pipeline such as filtering, mapping and rendering, as well as the optimization of the data structure. In the visualization of a time-varying dataset, data I/O processing occurs at every timestep of the dataset. Several methods of pre-fetching, parallel I/O and parallel pipeline processing have been developed as efficient data I/O techniques for time-varying visualization. In particular, parallel pipeline processing is widely used as an effective method that can reduce I/O bottlenecks and realize lower inter-frame delay. Remote visualization over a network enables users to utilize available computation resources and obtain visualization results on a desktop computer from the data that is retrieved from servers on the local network or over the Internet. In particular, distributed visualization, which is one of the configurations of remote visualization, is proposed in order to handle multiple datasets at remote sites. Collaborative visualization, also a configuration of remote visualization, allows multiple collaborative users to take part in several levels of visualization process. Finally, various visualization methods using leading edge environments are described. The utilization of massively parallel supercomputers and multiple GPU systems with tightly-coupled interconnecting backbones and a massive number of cores is effective to facilitate the faster visualization of larger datasets. In addition, virtual reality systems that enable users to interactively analyze such large-scale visualization results are also presented.

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  A test system for seafloor / borehole sensor, OOVEE (Oil Operated Virtual Environment Equipment), was equipped for long term sensor stability evaluation. OOVEE consists of two +/- 10 mK stability isothermo baths, a +/- 3 kPa stability (short term typical value) deadweight tester, and 6.6 L pressure chamber. The range of temperature is -2 to 175 degree Celcius, and of pressure 1 to 100 MPa. Pressure and temperature in the chamber were kept at 60 +/- 0.05 MPa and 2 +/- 0.008 degree Celcius for 22 hours evaluation. Variation of pressure came from acceleration of piston rotation, and more stable pressure can be supplyed within 2 hours. Temperature homogeniety of the isothermo bath was +/- 15 mK beneath 10 cm depth.

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  A series of laboratory experiments was performed on the shear strength of simulated gouge layers. The gouge layers were composed of quartz sand or calcite sand (particle size 0.125-0.250 mm) with 2 or 3 mm thickness. A stick-slip was occurred at the end of each experiment without exception because the upper block of the fault was pushed with a low stiffness spring. At the final stage of the experiments, a precursory slip and a dilatancy were observed prior to the stick-slip. This result and an experimental result using a photo-elastic material strongly suggest that stress chains (columnar structures with strong stresses) are created inside the gouge layer. They are gradually inclined to sustain the external additional shear force and finally rotated, lifting up the upper block. This seems to be the mechanism of the dilatancy in our experiments. The shear strength of the gouge layers is stronger for thinner layers than thicker layers and for calcite sand than quartz sand. These facts also suggest that the strength of stress chains determines the shear strength of the gouge layers. It will be a future problem whether this mechanism is applicable to the actual faults partly because of the fractal size distribution of fault gouge.

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  When using a dredge system for rock sampling from the ocean floor, it is important that the dredge system reach the desired location. However, using current systems it is difficult to know the exact position (latitude and longitude) of the dredge system. To better constrain the dredge position, we attached a small acoustic transponder to the observation wire, and attempted real-time monitoring of the dredge system's location during cruise MR08-06Leg-1b of the global ocean research vessel Mirai (R/V Mirai). Using the transponder's real-time location as displayed on the monitor screen of the acoustic navigation system on shipboard, we could precisely steer the vessel to direct the dredge along a path where rock exposures were expected by previous research. With this system we succeeded in collecting rock samples safely and reliably. Furthermore, subsequent analysis of information provided by the transponder allowed even more precise movement during towing of the dredge system.

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