Innovative Fibre-Optic Rotational Seismograph

Recent progress in rotational sensor technology has made it possible to directly measure rotational ground-motion induced by seismic waves. When combined with conventional inertial seismometer recordings, the new sensors allow one to locally observe six degrees of freedom (6DOF) of ground-motion, composed of three orthogonal components of translational motion and three orthogonal components of rotational motion. The applications of such 6DOF measurements are manifold—ranging from wavefield characterization, separation, and reconstruction to the reduction of non-uniqueness in seismic inverse problems—and have the potential to revolutionize the way seismic data are acquired and processed. However, the seismological community has yet to embrace rotational ground-motion as a new observable. The aim of this paper is to give a high-level introduction into the field of 6DOF seismology using illustrative examples and to summarize recent progress made in this relatively young field. It is intended for readers with a general background in seismology. In order to illustrate the seismological value of rotational ground-motion data, we provide the first-ever 6DOF processing example of a teleseismic earthquake recorded on a multicomponent ring laser observatory and demonstrate how wave parameters (phase velocity, propagation direction, and ellipticity angle) and wave types of multiple phases can be automatically estimated using single-station 6DOF processing tools. Python codes to reproduce this processing example are provided in an accompanying Jupyter notebook.

Section: Direct Observationsmentioning

confidence: 99%

Seismological Processing of Six Degree-of-Freedom Ground-Motion Data

Sollberger

Igel

Schmelzbach

et al. 2020

“…Physically each sensor can be divided into two basic parts: optical and electronic. The optical part, according to the schema in Figure 2, assures the Sagnac effect reversibility [17] and is constructed according to the description presented in our previous papers [11,13,15,19]. Only a substitution of a fiber coupler in loop and a piezoceramic phase modulator by a multifunction integrated optic chip (MIOC) (Idealphotonics Ltd., Shanghai, China) have been applied.…”

Section: Construction and Laboratory Investigation Of The Fiber-opmentioning

confidence: 99%

“…For the above reasons, this extended paper relates to a manuscript presented at the 7th International Symposium on Sensor Science (I3S2019) in Naples, Italy [15], in which we described the construction and laboratory tests, as well as results of field application of the set of two identical FOSREM ® —the innovative Fiber-Optic Rotational Seismograph. During the field test conducted in the geophysical observatory in Książ, Poland, torsion and tilt effects resulting from mining seismic quakes induced by copper mining operations have been recorded by them (FOSREMs) with high accuracy.…”

Section: Introductionmentioning

confidence: 99%

The Fiber-Optic Rotational Seismograph—Laboratory Tests and Field Application

Jaroszewicz

Kurzych

Krajewski

et al. 2019

Self Cite

The paper presents construction and laboratory tests, as well as the first field application of a new fiber-optic rotational seismograph. The system is based on a fiber-optic gyroscope (FOG), with determined Angle Random Walk of the order of 10−8 rad/Sqrt(s) and a few rad/s maximum detectable amplitude of rotation in the frequency range from direct current (DC) to 328.12 Hz. It has been designed for the rotational seismology area of interest. This work also presents exemplary relevant measurements, which were conducted using a set of two devices installed in the geophysical observatory in Książ, Poland.

“…Besides that, in most of the available seismic codes and numerical methods, the seismic load is defined as a clear translational ground motion, which describes the characteristic of Primary (P) and Secondary (S) body wave propagations through the ground. At the same time, the rotational load, generated mostly by Rayleigh (R) and Love (L) surface waves, as well as with body wave interactions with the ground surface [27], are neglected, mainly due to the lack of rotational measurements of the ground motion [28][29][30]. The significant development in six degrees of freedom (6-DoF) measurements of earthquakes and mining induced tremors has been noticed in the last 10 years when numerous essential research works have been reported in the field of development of new systems for integrated measurements of rotational and translational components of the ground motion [31][32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Validation of Rayleigh Wave Theoretical Formulation with Single-Station Rotational Records of Mine Tremors in Lower Silesian Copper Basin

Pytel

Fuławka

Mertuszka

et al. 2021

The classical Rayleigh surface rotational wave in terms of its theoretical notation and, resulting from this, properties associated with the induced seismic phenomena in mines are presented. This kind of seismic wave was analysed in-depth from the point of view of the parameters governing the form of its mathematical notation based on the similarity to the records obtained during the induced seismicity in near-field 6-DoF monitoring. Furthermore, conducted field measurements made it possible to relate the amount of the emitted seismic energy to the expected highest amplitude of rotational vibrations in the entire field of their impact on the rock mass. As a result, this made it possible to impose the completely defined R wave to the numerical models of given objects; the safety level, when subjected to the dynamic load induced by the rotational wave, would be an objective of the performed analyses. The conducted preliminary analyses were prepared for a plane strain state, for which the values of seismic rotations were evaluated concerning the energy and the distance of the seismic event’s source. As a result of the performed simulations, it was found that the results of the calculations matched with a satisfying degree with the field seismic measurements of the rotational ground motion induced by propagating the seismic wave. Such a verified analytical description of the theoretical formulas can be the basis for the implementation of R-wave characteristics into seismic codes and numerical analyses of object stability in the Lower Silesian Copper Basin region.