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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.

Show MeSH
The third model TSGG-72. The gyroscope using two tops improved the accuracy of the instrument’s vertical. The string gravity meter was the same as the second model. The gravity meter generated a great deal of gravity data through all the cruises of “Hakuho-maru” for nine years starting from 1974.
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fig4c: The third model TSGG-72. The gyroscope using two tops improved the accuracy of the instrument’s vertical. The string gravity meter was the same as the second model. The gravity meter generated a great deal of gravity data through all the cruises of “Hakuho-maru” for nine years starting from 1974.

Mentions: In 1972, we developed the third model TSSG-72 with a major revision in the gyroscope (Fig. 8). To improve the accuracy of the instrument’s vertical, an automated vertical gyroscope was produced by using two tops. The on-line data processing system was also improved with a new computer NOVA-01 that was small and convenient for on-line processing. Sampling interval of the vertical acceleration became 0.02 sec, and it was no longer necessary to correct the second order effect (Eq. [10]). Observed results were again recorded on paper tapes by using a teletypewriter as 8-bit data. Examples of the tapes are shown in Fig. 10. At that time, Mr. Hiromi Fujimoto (later, Professor at Tohoku University) conducted the system upgrade. Figure 11 shows the paper tapes piled up in front of a wall in our institute.


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

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

The third model TSGG-72. The gyroscope using two tops improved the accuracy of the instrument’s vertical. The string gravity meter was the same as the second model. The gravity meter generated a great deal of gravity data through all the cruises of “Hakuho-maru” for nine years starting from 1974.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4c: The third model TSGG-72. The gyroscope using two tops improved the accuracy of the instrument’s vertical. The string gravity meter was the same as the second model. The gravity meter generated a great deal of gravity data through all the cruises of “Hakuho-maru” for nine years starting from 1974.
Mentions: In 1972, we developed the third model TSSG-72 with a major revision in the gyroscope (Fig. 8). To improve the accuracy of the instrument’s vertical, an automated vertical gyroscope was produced by using two tops. The on-line data processing system was also improved with a new computer NOVA-01 that was small and convenient for on-line processing. Sampling interval of the vertical acceleration became 0.02 sec, and it was no longer necessary to correct the second order effect (Eq. [10]). Observed results were again recorded on paper tapes by using a teletypewriter as 8-bit data. Examples of the tapes are shown in Fig. 10. At that time, Mr. Hiromi Fujimoto (later, Professor at Tohoku University) conducted the system upgrade. Figure 11 shows the paper tapes piled up in front of a wall in our institute.

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