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

Bernauer, Felix; Behnen, Kathrin; Wassermann, Joachim; Egdorf, Sven; Igel, Heiner; Donner, Stefanie; Stammler, Klaus; Hoffmann, Mathias; Edme, Pascal; Sollberger, David; Schmelzbach, Cédric; Robertsson, Johan; Paitz, Patrick; Igel, Jonas; Smolinski, Krystyna; Fichtner, Andreas; Rossi, Yara; Izgi, Gizem; Vollmer, Daniel; Eibl, Eva P. S.; Buske, Stefan; Veress, Christian; Guattari, Frederic; Laudat, Theo; Mattio, Laurent; Sèbe, Olivie; Olivier, Serge; Lallemand, Charlie; Brunner, Basil; Kurzych, Anna T.; Dudek, Michał; Jaroszewicz, Leszek R.; Kowalski, Jerzy K.; Bońkowski, Piotr A.; Bobra, Piotr; Zembaty, Zbigniew; Vackář, Jiří; Málek, Jiří; Brokesova, Johana

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.