Studies of seafloor geodetic measurements on observation platforms adapted for sediments

适用于沉积物的观测平台的海底大地测量研究

• 批准号: 12440119
• 负责人: FUJIMOTO Hiromi
• 金额: $ 9.02万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440119/
• 关键词: seafloor geodetic measurement; observation of seafloor crustal movement; tilt measurement; ocean bottom pressure variation; precise point positioning; sedimentary layer; ocean bottom observation platform; deep-sea drill hole; 海底地穀変動; 日本海溝; 深海堀削孔

Subduction zones around Japan are covered with sediments, where precise geodetic measurements for observation of seafloor crustal movements can be difficult. This study aims at examining the stability of seafloor geodetic measurements on the sediments: tilt measurements on a platform with pipes installed in sefloor sediments, precise point positioning and observation of ocean bottom pressure variations with self-landing instrumentsWe have developed two sets of ocean bottom tiltmeter system for deployment by a remotely operated vehicle. The tiltmeter was divided into two parts for operation on the seafloor. A procedure for automatic leveling of the gimbals was improved to reduce consumption of the batteriesWe have confirmed resolution and stability of qaurtz pressure sensor through analysis of ocean bottom pressure data observed by three sensors over a spreading axis of the southern Pacific Rise for 14 manths in 1997-98. All of the sensors recorded pressure increase following the demise of the big 1997-98 El Nino event. The pressure variation suggests an ocean dynamics which can explain an abrupt change of J2 term of the Earth's gravity field. The results also suggest depression of the seafloor near the spreading centerIn July 2002 we could visually observe how a seafloor instrument for point positioning was deployed on the seafloor covered with thick sedimentary layer. The base of the instrument, 1m square of FRP mesh, looked quite stable and sunk only 1cm or less after deployment of 1year. We could confirm that we can carry out precise pressure monitoring and point positioning on thick sediments by using such a base

日本周围的俯冲带被沉积物覆盖，在其中很难观察到海底地壳运动的精确测量。这项研究旨在检查海底测量测量在沉积物上的稳定性：在平台上使用缝线沉积物中安装的管道，精确的点定位和使用自我地面仪器对海洋底部压力变化的精确点的定位和观察到了自我地面仪器的倾斜度测量。将倾斜表分为两个部分，用于在海底运行。通过分析1997 - 98年，通过分析三个曼特人的南太平洋上升轴的海洋底部压力数据，通过分析了三个传感器在南太平洋上升的扩散轴上观察到的海洋底部压力数据，确认了Qaurtz压力传感器的分辨率和稳定性。在1997 - 98年的El Nino事件消亡之后，所有传感器都记录了压力增加。压力变化表明海洋动力学可以解释地球重力场J2项的突然变化。结果还表明，2002年7月在扩散中心附近的海底凹陷，我们可以从视觉上观察如何将用于点定位的海底仪器部署在覆盖着厚厚的沉积层的海底。仪器的底部是1m正方形的FRP网眼，看起来很稳定，部署了1年后仅1厘米或更少。我们可以确认我们可以使用这样的底座进行精确的压力监测和点位置

项目成果

Nishimura,Miura et al.: "Distribution of seismic coupling on the subducting plate baundary"Tectonophysics. 323・. 217-238 (2000)

Nishimura、Miura 等：“俯冲板块边界上的地震耦合分布”Tectonophysicals 323・238（2000）。

Fujimoto, H.: "On the stability of horizontal positions of acoustic transponders for seafloor geodesy deployed on thick sediment"EOS Trans., AGU. 83・47. F354 (2002)

Fujimoto, H.：“关于部署在厚沉积物上的海底大地测量的声学转发器的水平位置的稳定性”EOS Trans.，AGU 83・47（2002）。

Kanazawa, T.: "Northwest Pacific Seismic Observatory and Hammer Drill Tests"Proc.ODP, Init. Repts.191,1-159:College Station TX 77845-9547,USA.. (CD-ROM). (2001)

Kanazawa, T.：“西北太平洋地震观测站和锤钻测试”Proc.ODP，Init。

Fujimoto, H.: "On the stability of horizontal positions of acoustic transponders for seafloor geodesy deployed on thick sediment"EOS Trans.AGU.. 83. G52A-0970 (2002)

Fujimoto, H.：“关于部署在厚沉积物上的海底大地测量的声学转发器水平位置的稳定性”EOS Trans.AGU.. 83. G52A-0970 (2002)

藤本博巳,友田好文: "重力からみる地球"東京大学出版会. 172 (2000)

Hiromi Fujimoto、Yoshifumi Tomoda：“从重力角度看地球”，东京大学出版社 172 (2000)。