Sagami Bay is known as a seismogenic area occurring large earthquakes repeatedly with M > 7 at the boundary between the Philippine Sea plate and the overriding northeastern Japan with the Quaternary sediments. To investigate this area for understanding the mechanism of repeated large earthquakes, we carried out a high density single-channel seismic reflection survey around Sagami Bay in April - May, 2005 using R/V Kaiyo of Japan Agency for Marine-Earth Science and Technology (JAMSTEC). We propose new growth scenario of a unique reverse fault associated with the 1923 Kanto earthquake in the Sagami Trough in this paper as follows from units of sedimentary layers of the seismic profiles provided tectonics information studies of the clear sedimentary facies is indicated along the Sagami Trough. In particular, the fault with reverse sense displacement of ENE-WSW strike is recognized in the Sunosaki Canyon. This reverse fault is located on the asperity of the large aftershock epicenter (M7.3) in the 1923 Kanto earthquake. There is no active fault in the seafloor of sedimentary layers from this reverse sense displacement to onshore. Thus, this displacement would be developed with the subducting Philippine Sea plate. We propose the growth process of obtained reverse sense displacement in Sagami Trough.

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Pre-stack depth migration (PSDM) of wide-angle seismic reflection and refraction survey data has a potential to image deep reflectors because the amplitude from a deep reflector becomes large at large offset. However, PSDM of wide-angle data has rarely been applied to the actual data because practical wide-angle surveys are usually too sparse to apply the PSDM. Seismic Interferometry (SI) can dramatically change the situation. By applying the SI to the wide-angle (OBS-airgun) data set, pseudo and dense receiver gathers can be generated. In this study, we generated pseudo receiver gathers by applying SI to the actual OBS-airgun data obtained in the North-Western Pacific region, and we tried to image oceanic Moho, which was about 12 km below the sea surface, by applying PSDM. We conducted a large number of parameter tests, and succeeded in imaging the oceanic Moho.

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Continuous analysis of the carbonate system in water surrounding calcifying organisms is an important technique in the study of calcification. Simultaneous measurement of pH and alkalinity is the most convenient way to describe the carbonate system in a water sample. These data are suitable for incubation experiments using small calcifying organisms because the water volume needed for analysis is small. In this report we describe a modified method focused on reduced volume (ca. 1 mL) samples based on the one-point titration method. The precision of this method, incorporating a correction using the masses of the water sample and added acid, is 0.1 - 0.2% (relative standard deviation). On the other hand, with no correction, the precision was 0.1 - 1.0% (relative standard deviation). Even though values showed a systematic error, precision was maintained through correction based on concurrent measurement of commercially available standards. This method allows us to describe the carbonate system in a small amount of water with sufficient precision and accuracy to investigate the mechanism of calcification using only a pH meter.

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JAMSTEC has a stock drum winch which was winded 8000 m class Optical - Electric composite armored cable (composite cable) for using Deep-Tow. In fiscal 2011, by using the composite cable, JAMSTEC conducted research cruise for 2011 Tohoku earthquake. But, an optical trouble was happened, and communication by using the composite cable became impossible between Deep-Tow and mother ship. On the other hand, this composite cable is necessary for great depth sea survey for example source zone survey of 2011 Tohoku earthquake. So conversion of composite cable is immediately required. Therefore the composite cable's renewal was done. Through the renewal, the optical loss budget was drawn for composite cable to be operated over 5000 m depths. It is confirmed that the optical loss of the underwater optical connector is within the range of the optical loss budget. The utilizable channel of this cable is improved from two channels to four channels. And the optical loss was also measured in operation during free-fall. In this paper, the author report above.

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We carried out underway geophysical survey in the transit of the JAMSTEC R/V Mirai MR08-06 Leg-1. The cruise was an unprecedented opportunity to collect data in regions of the Pacific Ocean where it has sparsely been surveyed. Our multibeam bathymetric and shipboard gravity survey track crossed over the Pacific, the Antarctic, and the Nazca plates, and covered lithospheric ages varying from zero to 150 Ma. The survey revealed kilometer-sized fine-scale structures of seafloor fabrics; i.e. abyssal hills and fracture zones, and distribution of seamounts or knolls. These are not detectable in satellite altimetry data only. As well as contributing to the world's seafloor mapping, our survey results also show valuable evidence towards the plate tectonic reconstruction and help us look into the oceanic lithosphere formation and evolution, since the directions of tectonic stress and seafloor spreading mode are the major factors that can affect the morphology of lineated abyssal hills, etc.

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