Rotation, Strain, and Translation Sensors Performance Tests with Active Seismic Sources

Abstract

Interest in measuring displacement gradients, such as rotation and strain, is growing in many areas of geophysical research. This results in an urgent demand for reliable and field-deployable instruments measuring these quantities. In order to further establish a high-quality standard for rotation and strain measurements in seismology, we organized a comparative sensor test experiment that took place in November 2019 at the Geophysical Observatory of the Ludwig-Maximilians University Munich in Fürstenfeldbruck, Germany. More than 24 different sensors, including three-component and single-component broadband rotational seismometers, six-component strong-motion sensors and Rotaphone systems, as well as the large ring laser gyroscopes ROMY and a Distributed Acoustic Sensing system, were involved in addition to 14 classical broadband seismometers and a 160 channel, 4.5 Hz geophone chain. The experiment consisted of two parts: during the first part, the sensors were co-located in a huddle test recording self-noise and signals from small, nearby explosions. In a second part, the sensors were distributed into the field in various array configurations recording seismic signals that were generated by small amounts of explosive and a Vibroseis truck. This paper presents details on the experimental setup and a first sensor performance comparison focusing on sensor self-noise, signal-to-noise ratios, and waveform similarities for the rotation rate sensors. Most of the sensors show a high level of coherency and waveform similarity within a narrow frequency range between 10 Hz and 20 Hz for recordings from a nearby explosion signal. Sensor as well as experiment design are critically accessed revealing the great need for reliable reference sensors.

Performance Test of the Rotational Sensor blueSeis-3A in a Huddle Test in Fürstenfeldbruck

“…The rotational and translational data were read, and time-shifts caused by the different time synchronization, time reference clocks, and low-pass filtering prior to digital sampling decimation were applied. The applied time-shifts, which maximize the correlation between vertical rotation rate and transverse acceleration, were −0.03 s for XB101, XB102, BS2, and XBLUE and −0.005 s for BS1, which are consistent with the values reported by Bernauer et al [ 6 ]. Subsequently, these data were merged, detrended, tapered, and filtered between 1 and 50 Hz.…”

“…Fiber-optic gyroscopes have started to be commonly used in the field of seismology (e.g., [ 5 , 6 , 7 , 8 , 9 ]). Portable blueSeis-3A sensors (iXblue, France), which are one of the first FOGs that only serve seismological purposes, allow for measuring three components of rotational motion with a high sensitivity in the broad frequency range from 0.001 to 50 Hz.…”

Performance of a Rotational Sensor to Decipher Volcano Seismic Signals on Etna, Italy

“…A study by Bernauer et al. (2021) obtained SNRs for the blueSeis‐3A around 200 calculating the RMS in a 1 s window for a close and explosive source. The SNR for a strong VT event is in a similar range.…”

Rotation Rate Sensors and Their Applications

“…For that reason, this Special Issue dedicates ten contributions to the testing and performance characterization of rotation sensors . Bernauer et al [ 10 ] describe a field experiment, which took place in Fürstenfeldbruck in November 2019, that was devoted to the comparison of 24 rotation rate sensors under artificially induced seismic excitations. The other three papers are devoted to more detailed field tests of particular devices during the Fürstenfeldbruck experiment: Kurzych et al [ 11 ], Izgi et al [ 12 ], and Brokešová et al [ 13 ].…”

“…Thus, rotational ground motion sensors provide a great opportunity to enhance the scientific output of seismic observations in various geophysical environments, from active volcanoes and the bottom of the ocean to glaciers or even extraterrestrial bodies (see, e.g., refs. [7,8,18,62] in the Special Issue by Bernauer et al [ 10 ]).…”