Development of sensor for measuring permanent displacement using servo-type velocity seismographs

地下管线等生命线的震害主要由地面变形引起，并伴有液化或滑坡。在修复的早期阶段，能够测量地面的变形来估计生命线系统的整体损伤是很重要的。但这次没有布置地表位移或液化的传感器，最近布置了许多伺服型速度地震仪。由于伺服地震仪的频率范围很宽，从0.02赫兹到70赫兹，地震仪可以从低频分量测量地面的永久位移。本研究的目的是开发一种新的方法，利用伺服地震仪来估计有效精度的地面永久位移。结果，可以理解，如果能够从记录中去除长周期分量中的地震信号，则可以估计永久位移。但仪器的偏角影响很大，本文提出了一种利用记录短周期范围内的相位特性来估计长周期信号的方法。采用群延时来表示地震运动的相位特征。我们提出了描述源过程的统计脉冲串模型。根据短周期地震运动分量的相位特征，可以在一定程度上估计出长周期信号。

The earthquake damages of the lifeline such as buried pipelines are caused mainly by deformation of ground that is accompanied with liquefaction or landslides. It is important that the deformation of ground can be measured to estimate total damage of lifeline system at the early stage of restoration. But the sensors of ground displacement or liquefaction are not arranged in this time.Recently many servo-type velocity seismographs are arranged. As the frequency range of a servo-type seismographs is very wide, from 0.02Hz to 70Hz, the seismographs may measure the permanent displacement of the ground from the component of the low frequency range.The purpose of this study is to develop new method to estimate permanent displacement of the ground in the effective precision using servo-type seismographsAt first the response of the seismographs is simulated against the ground motion which include permanent displacement. As the result it is understood that the permanent displacement can be estimated if the seismic signal in the long period component can be removed from the record. But the influence of declination of the instruments is found to be considerably large.The method for estimating long period signals is developed using phase characteristics in short period range of the record. Group delay time is adopted to represent phase characteristics of seismic motions. We proposed the stocastic impulse train model for representing source process. It is concluded that the long period signals can be estimated to some extent from the phase characteristics of a short period component of earthquake motion.