Research of crustal deformation at the plate boundary using GPS interferometry

全球定位系统干涉测量法用于调查板块边界的地壳变形。本研究旨在初步占领的网站和基础研究，以审查最佳的方法来应用该技术。1987年，进行了普查，并选择了南关东地区和北陆地区作为研究区域。从构造意义的角度来看，北陆地区受到了特别的关注，这里是Itoigawa-Shizuoka构造线，立山活火山和Atotsugawa活断层系统的所在地。1988年进行的第一次观测使用了WM 101单频接收机。今年的基线分析显示，短期重复性为百万分之一。为了通过减少电离层效应引起的误差来提高重复性，1989年使用了WM 102双频接收机。除宇治外，还在富山、金泽、上高良、立山、野边山设立了车站。这些台站的坐标是根据野边山VLBI站的共址而精确估算的。1989年的观测结果表明，重复性好得多，约为0.1ppm。对这些年进行了广泛的分析，发现了显著的场地位移。从富山、金泽、立山和上高良组成的菱形显示出面积扩展。而由富山、野边山和矢彦组成的大三角形则表现为南北向拉伸和东西向压缩。我们认为，再进行几年的复测，就可以弄清该地区的地壳形变。因此，一般来说，目前的全球定位系统测量和处理方法将在5年内重复进行全球定位系统测量时，在每年几厘米量级的阻滞板块运动方面产生足够的精度。

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.