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Introduction This is a briefing material for international media about the outline of R/V Natsushima research cruise around the epicenter, off Sumatra, 2004 Earthquake. It was published at Jakarta, March 28, 2005. In this material we show the result of our aftershock using ocean bottom seismograph and sea-bottom observation using remotely operated vehicle (ROV) at the thrust ridge of the trench ward boundary of the forearc where co-seismic uplift are inferred to be particularly high by the Sumatra-Andaman Earthquake of 26th December 2004. In the past, the giant earthquake of magnitude 9 classes was taken place in the deep water trench region after an interval of 40 years or more but it doesn't have any direct record to better understand displacement of the deep water sea bottom due to the earthquake, thus there are not a few examples of big tsunami like this time in the past. Clarifying displacement feature of the sea bottom as cause of the tsunami during and after the earthquake and explaining it are the obligations as the scientist when thinking the fact that life of approximately 300,000 peoples was lost due to this disaster. Our findings are important because we conducted the ROV survey just only two months after the great earthquake, therefore, pristine feature of sea bottom in the area being inferred to make big displacement, showing threat of the earthquake, has been well preserved. Here, we demonstrated three issues; results of bathymetric survey, of direct observation using ROV and of aftershock right after the great earthquake, 26th December, 2004. Such information is crucial for understanding seismic activity and mechanism for tsunami generation, and provides hint to the question where is a future tsunami source area in a deep-water environment in relation to an appropriate site selection for tsunami monitoring system to be built in future. Contents 1. Introduction (PDF 4.2MB) 2. Research facilities (PDF 3.3MB) 3. Outline of operations (PDF 8MB) 4. Result 1 (bathymetry) (PDF 3.8MB) 5. Result 2 (ROV observation) (PDF 5.1MB) 6. Result 3 (OBS) and Summary (PDF 3.5MB) |