CONSTRUCTION OF GRAVITY DATABASE OVER JAPANESE ISLANDS

在地球科学的广泛领域中，重力数据具有非常重要的意义和作用。例如，在大地测量学领域，它是精确确定大地水准面不可缺少的基本物理参数。因此，日本迫切希望建成全国性的重力数据库。最近，两个大型重力数据库相继发表。一个是重力数据库；日本重力光盘（GSJGDB）由日本地质调查局（现：国家先进工业科学技术研究所）于2000年出版。另一个是日本西南重力数据库（SWJGDB），这是我们日本西南重力研究组在2001年建立并发表的。日本西南地区重力数据库的主体框架是在发展前5个项目成果的基础上构建而成的(同类科研资助项目（1989-1991）No.01540331；1992-1994年04640400号1995-1997年编号07640552,1999-2000年编号11440130,2001-2003年编号13640428)通过这两个大型数据库的出版，日本重力数据库的情况有了很大的进展。通过将GSJGDB合并到我们的数据库中，我们编写了一个覆盖整个日本岛屿的新数据库（JGDB）。在JGDB的数据覆盖方面，仍存在部分空白或分布稀疏的地区，特别是在日本东北部。本项目的规划和执行有两个目标；(1)开始建设覆盖整个日本岛屿的发达的高精度重力数据库；(2)发布重力数据库获得的结果，并使其能够公开使用。所得结果如下：(1)在此期间，我们进行了广泛的重力调查，新补充的两万多份精确重力资料使东北西南地区西部的空白区完全消失。(2)利用这一有利条件，我们于2004年出版了东京大学出版社出版的《日本诸岛重力图集——日本西南部和日本中部》。除此之外，通过划分数据理想分布的区域，我们绘制了1/75,000比例尺的重力图。将该区域划分为7个区域，每个区域制作了4种图（a：站位分布图，b：布格异常图，c：彩色布格异常图，波长小于125km的彩色布格异常图）。少

In the wide area of the geo-sciences, gravity data have very important meanings and play an important role. In the field of geodesy, for example, it is indispensable fundamental physical parameter for precise geoid determination. Therefore, it was impatiently longed to be accomplished nationwide gravity database in Japan. Recently, two large gravity databases have been published successively. One is the gravity database ; Gravity CD-ROM of Japan (GSJGDB) by the Geological Survey of Japan (present : National Institute of Advanced Industrial Science and Technology) published in 2000. The other is the gravity database in Southwest Japan (SWJGDB) that constructed by our gravity research group in Southwest Japan and published in 2001. Main frame of the gravity database in Southwest Japan was constructed by developing the achievement of former five projects (the same category of Grant-in-Aid for Scientific Research: No.01540331 in 1989-1991,No.04640400 in 1992-1994,No.07640552 in 1995-1997,N … More o.11440130 in 1999-2000 and No.13640428 in 2001-2003). By publications of those two large databases, circumstances of the gravity database in Japan have much progressed. By merging GSJGDB into our database, we complied a new one to cover whole Japanese islands (JGDB). As concerned to the data coverage of JGDB, there still remained some parts of blank or sparsely distributed areas especially in the Northeast Japan.Present project was planed and executed with two aims ; (1) to start construction of a developed high precition gravity database to cover whole Japanese islands, (2) to issue results obtained by the gravity database and to make it possible for public use. The results obtained are as follows. (1) During the period concerned, we performed an extensive gravity survey and the blank area in the west of Southwest Tohoku district had completely disappeared by more than twenty thousands of newly supplemented precise gravity data. (2) By utilizing this desirable condition, we publish a gravity atlas "Gravity Atlas of Japanese Islands--Southwest Japan and Central Japan--" from the Univ. Tokyo Press in 2004. Besides this, by dividing areas where the data are desirably distributed, we drew 1/75,000 scale of gravity maps. The area were divided into 7 regions, and 4 kinds of maps (a : station distributions, b : Bouguer anomaly, c : colored Bouguer anomaly, and colored Bouguer anomaly of the wavelength less than 125km) were prepared for each regions. Less