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

这一研究项目的目的是开发全球定位系统，用于密集安装观测火山和活动断裂附近的地壳运动。为了实现这一点，系统应该具有高便携性和低功耗的规格，因为我们经常面临使用电力线和火山和活动断层附近的汽车通道的困难。1997年，我们测试了一款用于汽车导航系统的GPS接收板的性能，该板经过修改后用于载波相位差分GPS观测。从多次测试的结果来看，在测量距离小于10公里的情况下，该接收机的重复性小于5 mm，可以满足我们的要求。我们制作了由接收机和大容量记录系统(1 GB硬盘)组成的GPS观测系统样机。1998年，我们在震群活动非常活跃的静冈县伊藤市周围安装了10个样机系统。1998年4月20日，一场蜂群活动开始并持续了一个月左右。幸运的是，我们可以在高时间分辨率(采样1赫兹)的良好条件下获得数据。现在对数据进行了分析，并支持以下过程：1)就在震群活动开始后，Off-Ito下的裂缝开始打开。2)张开裂纹运动迅速增加，然后逐渐减小。3)随着裂隙的张开运动，较大地震(主要是M&GT；4)引起的位错运动与裂隙运动相加，继续在伊藤观测。并对1999年台湾集集地震震源区进行了时序观测，以检测其余震形变。

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.