Fibre Optic System for Monitoring Rotational Seismic Phenomena

Anna Kurzych,Zbigniew Krajewski,Krzysztof Teisseyre,Jerzy Kowalski,Leszek Jaroszewicz

doi:10.3390/s140305459

Abstract

We outline the development and the application in a field test of the Autonomous Fibre-Optic Rotational Seismograph (AFORS), which utilizes the Sagnac effect for a direct measurement of the seismic-origin rotations of the ground. The main advantage of AFORS is its complete insensitivity to linear motions, as well as a direct measurement of rotational components emitted during seismic events. The presented system contains a special autonomous signal processing unit which optimizes its operation for the measurement of rotation motions, whereas the applied telemetric system based on the Internet allows for an AFORS remote control. The laboratory investigation of such two devices indicated that they keep an accuracy of no less than 5.1 × 10−9 to 5.5 × 10−8 rad/s in the detection frequency band from 0.83∼106.15 Hz and protect linear changes of sensitivity in the above bandpass. Some experimental results of an AFORS-1 application for a continuous monitoring of the rotational events in the Książ (Poland) seismological observatory are also presented.

Highlights

Rotational seismic phenomena have been investigated theoretically for over thirty years [1]
In this paper we summarize our experiments on the construction, investigation and field application of the fibre optic interferometric device named Autonomous Fibre-Optic Rotational Seismograph (AFORS) [16]
The presented AFORS-1 system seems to be a promising device because it provides an opportunity for detecting absolute seismic rotation rates

Summary

Introduction

Rotational seismic phenomena have been investigated theoretically for over thirty years [1]. From the above mentioned conventional view, the existence of seismic rotational phenomena in grained rocks in a form of rotational events, as well as seismic rotational waves [3] has been studied in a few centres all over the world. In further consideration this property has been extended to rocks with microstructures or defects [4,5] or even any internal structure [6,7,8]. We distinguish two types of required rotation measurement systems: a ring laser [12], and a fibre-optic seismometer [13,14,15], both based on a technical implementation of the Sagnac interferometer

Objectives

Conclusion