2002 Fiscal Year Final Research Report Summary
Studies of seafloor geodetic measurements on observation platforms adapted for sediments
| Project/Area Number |
12440119
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
固体地球物理学
|
|---|
| Research Institution | Tohoku University |
|---|
Principal Investigator |
FUJIMOTO Hiromi Tohoku University, Graduate School of Science, Professors, 大学院・理学研究科, 教授 (50107455)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
KANAZAWA Toshihiko University of Tokyo, Earthquake Research Institute, Professor, 地震研究所, 教授 (30114698)
NISHINO Minoru Tohoku University, Graduate School of Science, Research Asociate, 大学院・理学研究科, 助手 (40322995)
MIURA Satoshi Tohoku University, Graduate School of Science, Associate professor, 大学院・理学研究科, 助教授 (70181849)
MOCHIZUKI Kimihiro University of Tokyo, EarthquMe Research Institute, Research associate, 地震研究所, 助手 (80292861)
KOIZUMI Kin-ichiro University of Tokyo, Ocean Research Institute, Research associate, 海洋研究所, 助手 (70107457)
|
|---|
| Project Period (FY) |
2000 – 2002
|
| Keywords | 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 |
|---|
| Research Abstract |
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 instruments
We 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 batteries
We 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 center
In 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
|
