Global scale sound speed field analysis by the ARGO data

ARGOシステムは，自動観測機（ARGOフロート）を全海洋に約3000台展開することにより地球規模の海洋変動を概ね300kmメッシュでリアルタイムに捉えることを可能とした観測網である。本研究では，このARGOシステムの水温・塩分/深度データから音速プロファイルを計算して，非常に広い海域における音速場の変動（平均音速，サウンドチャンネル軸など）を検知できる可能性について検証し，3.11の大地震における音速変動についても検出を試みた。その結果、ARGOデータ（水温，塩分）を用いることにより。ほぼリアルタイムで，地球規模の音速構造を解析できることを示した。例として，北西太平洋での解析を行い，多くのARGOフロートのデータから日本近海において複雑な軸深度構造が確認された。また，2011/3/11前後ARGOフロート12台のデータから音速プロファイルを計算し，震源域近傍を通過したフロートでは，大地震の後の音速の上昇のシグナルが認められた可能性を見出した。結果として，3,11のような突発的なイベントにおける海洋データ取得においては，常時グローバルに展開しているARGOシステムの有用性が再確認できた。第23回海洋工学シンポジウム「荒ぶる海、恵みの海」（2012年8月2日～3日, 日本大学駿河台キャンパス

地球環境変動に伴う海洋音波伝搬減衰の長期変化

発表番号: 15-19 / 海洋音響学会2015年度研究発表会（2015年5月14日～15日, 東京大学） / 海洋音響学会2015年度研究発表会講演論文集から転

Change of Sound Speed Profile in the Epicenter near the Large-scale Undersea Earthquake Observed by Ocean Observation Float

The Tohoku region Pacific Ocean earthquake that occurred on March 11, 2011, resulted in extensive damage in a vast area ranging from the Tohoku to Kanto. However, at the time of the earthquake, no research vessel was confirmed to be investigating marine life in the seas adjacent to epicenter area, so physical data like water temperature and salinity, as well as ocean sound speed data required for the echo sounder, could not be acquired. Therefore, in this study, we compute the sound speed profile from the Argo system data(water temperature, salinity, pressure) that was being deployed near the area of the epicenter both before and after the earthquake, and attempt to detect the change in the sound speed field. In addition, the Tohoku region Pacific Ocean earthquake and the Sumatra earthquake in December 2004, which were accompanied by a giant tsunami, were also investigated. Results showed that in the main temperature front between the central thermocline and deep-sea isothermal layer, water temperature did not change very much. However, we confirmed the tendency for the underwater sound speed to suddenly increase dramatically after an earthquake

地震前後におけるアルゴフロートを用いた海洋物理データ収集の研究

Tohoku region Pacific Ocean earthquake that occurred on March 11, 2011, resulted in extensive damage to vast areas rangingfrom the Tohoku to Kanto. However, at the time of an earthquake occurrence, the research vessel which was researching aboutmarine in earthquake hypocenter area adjacent seas is not confirmed, and ocean physical data like water temperature or salinityincluding ocean sound speed data required for echo sounder etc. cannot be acquired. Therefore, paying attention to the oceanautomatic profiling system (Argo system) in this study. Currently, Argo float has deployed about 3600 units in all the worldocean. Thus, it does not require large-scale observation system by research ship or tethered buoy. And we became able to graspthe marine structure of the scale of the earth immediately and easily.In this study, tried the acquisition of ocean physical data from the Argo data (water temperature, salinity, pressure) which unfolded before and after an earthquake near the focal area. As a result, In this earthquakes associated with the huge tsunami,rapid water temperature change has been confirmed in the vicinity of the sea after the earthquake.In addition, we analyzed about Sumatra offing earthquake accompanied by a similar huge Tsunami. Data was acquired fromtwo Argo floats which was observation in the seismic center area of ocean in 2005. As a result, a few days after the tsunamioccurrence, the thing by which the ocean physical data indicates a profile different from usual was suggested. Thus, to variationsin sudden marine environment, Argo system has been shown to be one of the effective database.SSS02-04発表要旨 / 日本地球惑星科学連合2015年大会（2014年5月24日～5月28日, 幕張メッセ国際会議場） / 日本惑星科学連合の許諾に基づき本文ファイルを掲

ARGOデータによる北西太平洋の音速場解析

発表番号: 11-03 / 海洋音響学会2011年度研究発表会（2011年5月30日～31日） / 海洋音響学会2011年度研究発表会講演論文集から転

南極海における長距離音波伝播の越冬観測

In this paper, long-term observation in the AntarcticOcean using newly developed profiling float for deep sea"Deep NINJA", it succeeded in the deep sea profilingobservation under the winter sea ice for in about sixmonths for the first time in the world. From the dataobtained by this, it was analyzed for ocean soundthat depth of up 4,000 m in under winter ice inthe Antarctic Ocean. In the place deeper than2,000m that was not observed by the Argo float,it was found that variations in salinity and watertemperature is small, and does not affect thesound speed changes therefore. Moreover, in thesea surface, it succeeded in capturing clearseasonal variation in the freezing season and thethawing season. Therefore, the possibility thatthe sound propagation path and the signal levelis different depending on the season was found inthe shallow sea area of Antarctic Ocean. Fromthis, the possibility to affect the predation actionsof passive sonar or marine mammals is thought about.Poster 3P6-1, The 35th Symposium on Ultrasonic Electronics (3-5 December 2014, Meiji University, http://www.use-jp.org/j/) / 第35回超音波エレクトロニクスの基礎と応用に関するシンポジウ

Sound Speed Structure Long-term Monitoring in Antarctica by the Deep-sea Automatic Observation Float

Indirect observation to convert the sound speed has been carried out as a method of observing the ocean acoustic environment from water temperature and salinity observed in the mooring buoy and ship observations. However, there is a problem in that these have both high initial cost and running cost. Therefore, to address these issues, a study of the wide area ocean sound observation system using the observation data from a marine automatic observation float was performed. To capture in detail the changes in the ocean acoustic environment due to recent climate change, however, it is necessary to observe areas of the deep sea that can not be detected by Argo floats. Also, during the season when the Antarctic Ocean is frozen, continuous observation data of the deep sea cannot be acquired, and water temperature, salinity, and sound speed structure are not clear. As a result, JAMSTEC developed a new profiling float, called the “Deep NINJA” for deep-sea observations. The float was subjected to a yearlong monitoring of the Antarctic Ocean off the Adelie Coast in 2012. For the first time, it succeeded in monitoring long-term the sound speed profile to a depth of 4000 m in the Antarctic Ocean, and was able to capture a seasonal change in the surface area in the freezing and thawing seasons. In addition, by calculating sound speed from these data, simulations were performed assuming low-frequency sonar. The results obtained the ingredient that propagates while repeating a reflection in the extremely small layer of the sea surface neighborhood, and the ingredient that propagates while being reflected near a water depth of 100 m, which changes the sound speed gradient. From this, propagation loss was found to be smaller in winter than summer, and the possibility that a sound wave would propagate to a more distant place was demonstrated. This may affect the long-distance sound wave propagation of the echolocations of passive sonar and marine mammals

Development of Tension-Torsion Multiaxial Creep Testing Apparatus for Heat Resisting Steel

This paper describes development of a combined tensiontorsion multiaxial creep testing apparatus for heat resisting steel. It is essential for high temperature component designing to investigate creep rupture life and creep properties of heat resisting steel. Although high temperature structural components undergo multiaxial stress damage due to complex loading situation or shape discontinuity of the actual structure, there is no commercial testing apparatus which can conduct a creep testing under multiaxial stress conditions. In this study, we developed a combined tension-torsion multiaxial creep testing apparatus which can apply multiaxial stress to a hollow cylinder type testing specimen with 6 kN axial load and 12 Nm torsional load at high temperatures. Since the testing apparatus also has measuring devices for axial and shear displacements of the specimen, relationship curve between testing time and equivalent strain under multiaxial stress conditions of type 304 stainless steel is also discussed