Report of Hydrographic And Oceanographic Researches

No.41 (March, 2005)
[ Previous ] [ List ] [ Next ]

Contents

Entire documentsEntire documents

Original Papers

  1. abstract pdf Bouguer Gravity anomalies(ver. 2004) of Japanese Island Arcs and its adjacent seas
    Yoshio Ueda , p.1
  2. abstract pdf Inverse method and precision improvement for seafloorpositioning
    Tadashi Ishikawa and Masayuki Fujita , p.27
  3. abstract pdf Distributions of Sedimentary POPs(Persistent Organic Pollutants) in Tokyo Bay -Results from the Survey of POPs in Tokyo Bay in 2002.
    Junko SHIMIZU and Satoshi YAMAO, Takuma NOSAKA, Ken-ichi Noguchi, Masayuki MINE, Keizo MATSUMOTO, Kazuyoshi OICHI, Kazunao TSUTSUMI, Tetsuji MIYAMOTO and Yoshiro IKEDA , p.35
[ Previous ] [ List ] [ Next ]

Abstracts

Bouguer Gravity anomalies(ver. 2004) of Japanese Island Arcs and its adjacent seas

Yoshio Ueda

The Hydrographic and Oceanographic Department of Japan have been conducted marine gravity surveys since 1965. Based on theses survey results, precise Bouguer gravity anomaly maps of the Japanese Island arcs and its adjacent seas were compiled by a newly developed?terrain?correction method (Ueda, 2003). Topographic mesh data with the size of 10h x 10h are used as basic mesh data for the terrain corrections of marine gravity survey data with line spacing about 2 mile or less, and 30h x 30h size mesh data for the marine gravity survey data at a scale of 1/500,000. For interpolations of the depths within a rectangular area defined by the 4 basic mesh data points, a weighted gradient interpolation method was used. Japanese island arcs and its adjacent continental shelf regions are covered by 6 sheets of Lambertfs conformal conic projection maps. Besides, the small scale gravity anomaly maps covering whole Japanese islands and its adjacent seas including the Shikoku basin, west Philippine sea , and the northwestern part of the Pacific ocean are also compiled in two sheets. @@

Inverse method and precision improvement for seafloorpositioning

Tadashi Ishikawa and Masayuki Fujita

For the precise GPS/Acoustic seafloor positioning, we are developing an analysis software, which combines a kinematic GPS result and an observed acoustic travel time to get a precise position of an array of seafloor stations.

We summarize the method of this analysis, especially focusing on estimation of underwater sound velocity structure.

In this analysis,vertical coordinates of seafloor stations and the sound velocity are not completely independent. Therefore vertical coordinates are greatly influenced by the error of sound velocity and in consequence their precision is more deteriorated than that of horizontal coordinates.

So we present a new analysis strategy for precision improvement. In this strategy the vertical coordinates are no longer estimated values, but are fixed at known values. This strategy improves the estimation of sound velocity.

As a result, the precision of estimated coordinates ofseafloor stations got improved for the horizontal components.

Distributions of Sedimentary POPs(Persistent Organic Pollutants) in Tokyo Bay -Results from the Survey of POPs in Tokyo Bay in 2002.

Junko SHIMIZU and Satoshi YAMAO, Takuma NOSAKA, Ken-ichi Noguchi, Masayuki MINE, Keizo MATSUMOTO, Kazuyoshi OICHI, Kazunao TSUTSUMI, Tetsuji MIYAMOTO and Yoshiro IKEDA

In 2002, vertical and horizontal distributions of POPs in Tokyo Bay were surveyed by Hydrographic and Oceanographic Department, Japan Coast Guard. The samples were analyzed about thirteen kinds of POPs. The sedimentation dating of core samples were analyzed based on 210Pb measurements.

In the horizontal distributions of POPs, most of substances show highest concentration points on the head of the bay, next higher points were on the entrance of the bay, and the lowest points were near the Naka-no-se and Uraga-Suido traffic routes. The concentrations of each substance on the head of Tokyo Bay were compared. PCBs and most of the substances show the higher concentration in the west part than the east part of the bay.

On the other hand some components of Dioxins, PCDDs and PCDFs, show the higher concentrations in the east part than the west part. Characteristics of these surface distributions are considered to be related to the source of the substances and/or the sedimentation environment such as the grain size.

Historical trend of POPs was considered from the vertical distributions of POPsf concentration. The concentrations of PCBs and most of the substances began rising at 1950s, showing the peak near 1970, and then lowering until today. The concentration of Chlordanes showed the peak at 1980s, and relatively high concentrations were kept until today. The concentration of HCB began rising at 1950s, and relatively high concentrations were kept until today. The historical trends of the concentrations were considered to be reflected the terms of use and/or discharge of each substance.

[ Previous ] [ List ] [ Next ]