Development of the portable and low power GPS system for geodetic observations near volcanoes and active faults

这个研究项目的目的是开发GPS系统，以便密集地观测火山和活动断层附近的地壳运动。为了实现这一目标，系统应该具有高便携性和低功耗的规格，因为我们经常面临在火山和活动断层附近使用电力线路和汽车可达道路的困难。1997年，我们研究了一种用于汽车导航系统的GPS接收板的性能，并对其进行了修正，用于载波相位差GPS观测。从多次测试的结果来看，在测量距离小于10km的情况下，该接收机的重复性小于5mm，可以满足我们的目的。我们制作了GPS观测系统样机，该系统由接收机和大容量存储（1GB硬盘）的记录系统组成。1998年，我们在静冈县伊藤市附近安装了10个原型系统，那里地震群活动非常频繁。1998年4月20日，蜂群活动开始并持续了大约一个月。幸运的是，我们可以在高时间分辨率（采样1Hz）的良好条件下获得数据。现在对数据进行分析，并支持以下流程；1)就在地震群活动开始后，Off-Ito下面的裂缝开始裂开。2)张开裂纹运动迅速增大，但逐渐减小。3)在裂缝张开运动的同时，还增加了大地震（主要是M bbbb4）引起的位错运动。我们在伊藤继续观察。并在1999年台湾集集地震震源区进行了时间观测，以探测其余震变形。

The aim of this research project is developing the GPS system for densely installed observation of the crustal movement near volcanoes and active faults. To realize it, the system should have the specification of high-portability and low-power consumption, because we often face difficulties to use the electric power line and automobile-accessible roads near volcanoes and active faults.In 1997, we examined the performance of a GPS receiver board for automobile navigation system, which are revised for carrier phase differential GPS observation. From the results of several examinations, it proved that the repeatability of the receiver was less than 5mm in the case that the measurement distance is less than 10km, and the receiver was available for our purpose. We made prototype of the GPS observation system composed of the receiver and a recording system with huge memory (1GB hard-disk).In 1998, we installed ten prototype systems around Ito city, Shizuoka prefecture where the earthquake swarm activity is very high. On April 20, 1998, a swarm activity began and lasted around one month. Fortunately, we could get the data in good conditions of high time resolution (sampling 1Hz). The data is now analyzed, and support the following processes ; 1) A crack beneath Off-Ito began to open, just after the earthquake swarm activity started. 2) The opening crack movement increased rapidly and decreased gradually. 3) Accompany with the opening crack movement, the dislocation movement caused by the grater earthquakes (mainly M>4) are added with the movement.We continue the observation at Ito. And we started the temporal observation at the focal region of 1999 Chi-chi earthquake in Taiwan for detecting the aftershock deformation of it.