Research of crustal deformation at the plate boundary using GPS interferometry

利用GPS干涉测量技术研究了板块边界的地壳形变。本研究的目的是为了研究应用该技术的最佳方法的场地的初始占领和基础研究。1987年，进行了勘察调查，选定了关东南部地区和北国地区作为研究区。从构造意义的角度特别关注北国地区，那里有Itoigawa-Shizuoka构造线、Tateyama活火山和Aotsugawa活动断裂系统。1988年进行的第一次试验使用了WM101单频接收器。这一年的基线分析显示，短期可重复性约为PERT/百万。为了通过减少电离层效应的误差来提高重复性，WM102双频接收机于1989年投入使用。除了Uji之外，还在富山、金泽、龟谷原、竹山、野山建立了车站。这些站点的坐标是根据Nobeama VLBI站点的位置进行精确估计的。1989年的观测表明，重复性要好得多，重复性在0.1ppm左右。对这些年进行了广泛的分析，发现了显著的场地位移。由富山、金泽、玉山、龟谷原组成的菱形呈面状延伸。而由富山、野山和八彦组成的大三角则表现为N-S伸展和东西向挤压。我们认为，再重复几年，就能弄清该地区的地壳形变。因此，一般来说，目前的GPS测量和处理方法将在重复GPS测量的5年内，产生足够的精度来分离每年几厘米量级的板块运动。

GPS interferometry is applied to investigate crustal deformation at plate boundaries. The present study aimed at initial occupations of sites and fundamental research for examining the best approach to apply the technique. In 1987, reconnaissance surveys were made and the South Kanto area and the Hokuriku area were selected as study area. Hokuriku area was put special attention from the standpoint of tectonic significance, where Itoigawa-Shizuoka tectonic line, Tateyama active volcanoes and Atotsugawa active fault system are located. The initial occpation conducted in 1988 employed WM101 single frequency receivers. Baseline analysis at this year showed short-term repeatability in the order of pert per million. In order to improve the repeatability by reduction of errors due to ionospheric effects, WM102 dual frequency receivers were used in 1989. Stations at Toyama, Kanazawa, Kamitakara, Tateyama, Nobeyama in addition to Uji were established. Coordinates of these stations were precisely estimated based on the colocation at the Nobeyama VLBI site. Observation in 1989 showed much better repeatability in the order of 0.1ppm. Extensive analyzes of these years have been executed and significant site displacements were found. Rhombus that consisted from Toyama, Kanazawa, Tateyama and Kamitakara showed areal extension. On the other hand, large triangle which is made up from Toyama, Nobeyama and Yahiko showed N-S Extension and E-W compression. We suggest that a few more years of repetition will clarify the crustal deformation in the area. Thus, generally speaking, the present way of GPS measurements and processing would result in enough accuracy in detencing plate motions of the order of a few cm's a year by within 5 years of repeated GPS measurements.