6C Recordings at Active Volcanoes

Near field recordings and thus finite source inversions of volcano-induced events often suffer from unaccounted effects of local tilt, saturation of classical instrumentation, unknown shallow velocity structure and doubtful orientation of the instruments. In addition, if the station number is limited the results of moment tensor inversions are very often not well constrained. Recent advances in hardware development made it possible to install several very broadband, high sensitive rotational motion sensor, based on fibre optical gyroscope technology, in very close distance of an activate volcano, i.e. on Stromboli volcano in 2016 and 2018, respectively. Using this new instrument together with classical instrumentation (i.e., translational seismometer, infra sound and tilt meter) we were able to record four weeks of permanent strombolian activity at Stromboli during these two experiments. The resulting six axis measurements reveal clear rotations around all three coordinate axis. We are furthermore able to demonstrate how this six axis measurements can help to improve the location procedure due to the property of a fiver optic gyro to act as a physical wave polariser. We also demonstrate the application of a single site shallow velocity estimation using volcanic background noise only, which will further improve the reliability of the source mechanism estimate. As a concluding step we will demonstrate how the use of sparse 6C measurement might be able to reduce the ambiguity of moment tensor inversions of volcano related signals.PublishedSan Francisco (CA)8T. Sismologia in tempo real

Use of Rayleigh-OFDR to estimate the bias drift induced by quasi-static and homogeneous temperature variation of a free-standing fiber-gyro coil

International audienc

BlueSeis3A: Full Characterization of a 3C Broadband Rotational Seismometer

Recently, due to observations of rotational ground motions, a promising new field of research in seismology and engineering has developed. However, exploration of rotation’s potential has been hampered by the lack of a portable, reliable, and highly sensitive broadband rotational ground‐motion sensor. In this work, we present laboratory tests of the BlueSeis3A, the first commercially available fiber‐optic gyroscope specifically designed for applications in broadband seismology. Here, we estimate the sensor’s self‐noise level by means of power spectral density, operating range diagrams, and Allan deviation. Scale factor linearity is measured up to the largest likely rotation rates in seismology (⁠∼900  mrads−1⁠). Tests of the sensor’s susceptibility to changes in ambient conditions, such as temperature or magnetic field, demonstrate the BlueSeis3A’s reliability in field installations. Estimation of the orthogonality of the three sensor components completes our tests. We conclude that the BlueSeis3A is fit for a wide range of field applications in seismology, volcanology, ocean‐bottom observations, and earthquake engineering

Exploring planets and asteroids with 6DoF sensors: Utopia and realism

A 6 degrees-of-freedom (6DoF) sensor, measuring three components of translational acceleration and three components of rotation rate, provides the full history of motion it is exposed to. In Earth sciences 6DoF sensors have shown great potential in exploring the interior of our planet and its seismic sources. In space sciences, apart from navigation, 6DoF sensors are, up to now, only rarely used to answer scientific questions. As a first step of establishing 6DoF motion sensing deeper into space sciences, this article describes novel scientific approaches based on 6DoF motion sensing with substantial potential for constraining the interior structure of planetary objects and asteroids. Therefore we estimate 6DoF-signal levels that originate from lander–surface interactions during landing and touchdown, from a body’s rotational dynamics as well as from seismic ground motions. We discuss these signals for an exemplary set of target bodies including Dimorphos, Phobos, Europa, the Earth’s Moon and Mars and compare those to self-noise levels of state-of-the-art sensors.Horizon 2020 http://dx.doi.org/10.13039/501100007601Projekt DEA

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

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.ISSN:1424-822