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，发挥着重要作用。例如，在大地测量领域，它是精确确定大地水准面不可或缺的基本物理参数。因此，日本迫切希望在全国范围内实现重力数据库。最近，两个大型重力数据库相继问世。一个是重力数据库，由日本地质调查局(现：国家先进工业科学技术研究所)于2000年出版的日本重力光盘。另一个是我们在日本西南部建立的重力数据库(SWJGDB)，它是由我们的重力研究组在2001年建立的。日本西南部重力数据库的主要框架是在前五个项目成果的基础上构建的(同类科研资助项目：-1991年第01540331号，1992年-1994年第04640400号，1995年-1997年第07640552号，N…1999-2000年的11440130号和2001-2003年的13640428号)。随着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步。通过将GSJGDB合并到我们的数据库中，我们编译了一个覆盖整个日本岛屿的新数据库(JGDB)。关于JGDB的数据覆盖，仍有一些空白或稀疏分布的地区，特别是在日本东北部。现有的项目是为了两个目标：(1)开始建设一个已开发的高精度重力数据库，覆盖整个日本岛屿；(2)发布重力数据库的成果，并使其能够供公众使用。取得的结果如下。(1)在此期间，我们进行了广泛的重力测量，西南东北地区西部的空白区域已经被2万多个新补充的精密重力数据完全消失了。(2)利用这一有利条件，我们从大学出版了《日本群岛--日本西南和日本中部--重力地图集》。2004年，东京出版社出版。此外，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。将该区划分为7个区，分别编制了4种布格异常图(a：台站分布图、b：布格异常图、c：布格彩色异常图、125 km以下布格彩色异常图)。较少

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