BlueSeis3A: Full Characterization of a 3C Broadband Rotational Seismometer

Abstract

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 (similar to 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.