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Gravity at sea--A memoir of a marine geophysicist.

Tomoda Y - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2010)

Bottom Line: Professor Chuji Tsuboi made a number of unsuccessful attempts at developing a gravity meter that can be operated on a normal surface ship by reducing the noise by minimizing the motion of the gravity meter through a mechanical design.I have chosen a new approach toward the measurements of gravity on a surface ship by simplifying the mechanical part using a string gravity meter that was installed directly on a vertical gyroscope in combination with the numerical and/or electronic reduction of noises.The results reveal the fine structures of gravity field in and around trenches that provide important clues as to a number of geodynamic issues including the nature of the trench-trench interaction and the interaction of trenches with seamounts.

View Article: PubMed Central - PubMed

Affiliation: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan. fujimoto@aob.gp.tohoku.ac.jp

ABSTRACT
A history of studies on the gravity measurements at sea in Japan is reviewed with an emphasis on the contribution of the author. The first successful measurements at sea were made in 1923 by Vening Meinesz in the Netherlands using the pendulum apparatus installed in a submarine. However, the gravity measurements using a submarine are not convenient because the access to a submarine is limited. Professor Chuji Tsuboi made a number of unsuccessful attempts at developing a gravity meter that can be operated on a normal surface ship by reducing the noise by minimizing the motion of the gravity meter through a mechanical design. I have chosen a new approach toward the measurements of gravity on a surface ship by simplifying the mechanical part using a string gravity meter that was installed directly on a vertical gyroscope in combination with the numerical and/or electronic reduction of noises. With this gravity meter TSSG (Tokyo Surface Ship Gravity Meter), we firstly succeeded in measuring gravity at sea onboard a surface ship in July 1961 and the measurements have been extended to the northwestern Pacific and beyond. The results reveal the fine structures of gravity field in and around trenches that provide important clues as to a number of geodynamic issues including the nature of the trench-trench interaction and the interaction of trenches with seamounts.

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The gravity pendulum and Professor Motonori Matuyama. The Meinesz’s pendulum apparatus placed in the commanding tower of the Japanese submarine “Ro 57”. On the right is Professor Motonori Matuyama, and on the left is Naoichi Kumagai (technical associate at that time). The submarine set sail from Yokosuka naval port in a drizzle on October 17, 1934. The team measured three or four dives a day, 27 times during a total 25 dives crossing the Japan Trench six times.
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fig2b: The gravity pendulum and Professor Motonori Matuyama. The Meinesz’s pendulum apparatus placed in the commanding tower of the Japanese submarine “Ro 57”. On the right is Professor Motonori Matuyama, and on the left is Naoichi Kumagai (technical associate at that time). The submarine set sail from Yokosuka naval port in a drizzle on October 17, 1934. The team measured three or four dives a day, 27 times during a total 25 dives crossing the Japan Trench six times.

Mentions: The gravity measurement at sea was also advanced in Japan. The Sanriku district in the northeast Japan was flooded by a “Tsunami” due to an earthquake that occurred in the Japan Trench off the district in March 1933. In the next year, “the Geodetic Committee of Japan” imported the Meinesz’s apparatus from the Netherlands (Fig. 2). Professor Motonori Matuyama installed the device on a Japanese submarine as is shown in Fig. 3 and measured the gravity around the Japan Trench.4) Figure 4 shows the submarine “Ro-57”. He also measured the gravity over the Izu–Ogasawara Trench in the following year. I have deep respect to Professor Matuyama for determining the gravity distribution of the island arc and the trench system around Japan, about ten years after Vening Meinesz invented the apparatus.


Gravity at sea--A memoir of a marine geophysicist.

Tomoda Y - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2010)

The gravity pendulum and Professor Motonori Matuyama. The Meinesz’s pendulum apparatus placed in the commanding tower of the Japanese submarine “Ro 57”. On the right is Professor Motonori Matuyama, and on the left is Naoichi Kumagai (technical associate at that time). The submarine set sail from Yokosuka naval port in a drizzle on October 17, 1934. The team measured three or four dives a day, 27 times during a total 25 dives crossing the Japan Trench six times.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3037522&req=5

fig2b: The gravity pendulum and Professor Motonori Matuyama. The Meinesz’s pendulum apparatus placed in the commanding tower of the Japanese submarine “Ro 57”. On the right is Professor Motonori Matuyama, and on the left is Naoichi Kumagai (technical associate at that time). The submarine set sail from Yokosuka naval port in a drizzle on October 17, 1934. The team measured three or four dives a day, 27 times during a total 25 dives crossing the Japan Trench six times.
Mentions: The gravity measurement at sea was also advanced in Japan. The Sanriku district in the northeast Japan was flooded by a “Tsunami” due to an earthquake that occurred in the Japan Trench off the district in March 1933. In the next year, “the Geodetic Committee of Japan” imported the Meinesz’s apparatus from the Netherlands (Fig. 2). Professor Motonori Matuyama installed the device on a Japanese submarine as is shown in Fig. 3 and measured the gravity around the Japan Trench.4) Figure 4 shows the submarine “Ro-57”. He also measured the gravity over the Izu–Ogasawara Trench in the following year. I have deep respect to Professor Matuyama for determining the gravity distribution of the island arc and the trench system around Japan, about ten years after Vening Meinesz invented the apparatus.

Bottom Line: Professor Chuji Tsuboi made a number of unsuccessful attempts at developing a gravity meter that can be operated on a normal surface ship by reducing the noise by minimizing the motion of the gravity meter through a mechanical design.I have chosen a new approach toward the measurements of gravity on a surface ship by simplifying the mechanical part using a string gravity meter that was installed directly on a vertical gyroscope in combination with the numerical and/or electronic reduction of noises.The results reveal the fine structures of gravity field in and around trenches that provide important clues as to a number of geodynamic issues including the nature of the trench-trench interaction and the interaction of trenches with seamounts.

View Article: PubMed Central - PubMed

Affiliation: Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan. fujimoto@aob.gp.tohoku.ac.jp

ABSTRACT
A history of studies on the gravity measurements at sea in Japan is reviewed with an emphasis on the contribution of the author. The first successful measurements at sea were made in 1923 by Vening Meinesz in the Netherlands using the pendulum apparatus installed in a submarine. However, the gravity measurements using a submarine are not convenient because the access to a submarine is limited. Professor Chuji Tsuboi made a number of unsuccessful attempts at developing a gravity meter that can be operated on a normal surface ship by reducing the noise by minimizing the motion of the gravity meter through a mechanical design. I have chosen a new approach toward the measurements of gravity on a surface ship by simplifying the mechanical part using a string gravity meter that was installed directly on a vertical gyroscope in combination with the numerical and/or electronic reduction of noises. With this gravity meter TSSG (Tokyo Surface Ship Gravity Meter), we firstly succeeded in measuring gravity at sea onboard a surface ship in July 1961 and the measurements have been extended to the northwestern Pacific and beyond. The results reveal the fine structures of gravity field in and around trenches that provide important clues as to a number of geodynamic issues including the nature of the trench-trench interaction and the interaction of trenches with seamounts.

Show MeSH