Multicomponent acquisition systems today record incomplete data because they do not measure rotations. Geophones or accelerometers provide linear motion and hydrophones provide pressure, but no current commercial acquisition system includes sensors that measure rotations. Without rotations, the data provide incomplete recording of the wavefield because in three dimensions, there are six degrees of freedom -three linear displacements and three rotations. In two small 2D seismic surveys recorded with six components, three-component geophones were deployed and three-component rotation sensors that measured pitch, roll, and yaw were deployed. Pitch was measured independently with closely spaced geophones. Measuring rotations with closely spaced geophones is not practical in production, but it can be used in research and development to validate rotationsensor data. A comparison of pitch measured by two independent methods finds that they fit after instrument designature. Data provided by rotation sensors have additional value because they can be used in analysis of singular value decomposition (SVD) to identify and separate ground roll and body waves.
Most of the current rotational sensing technology is not geared toward the recording of seismic rotations' amplitudes and frequencies. There are few instruments that are designed for rotational seismology, and the technology for building them is currently being developed. There are no mass industrial producers of seismic rotation sensors as there are for geophones, and only one current sensor model can be deployed on the ocean bottom. We reviewed some current rotationalseismic acquisition technologies, and developed a new method of recording rotations using an existing, robust and fielddeployable technology that had seen extensive use in large exploration surveys: induction-coil magnetometers. We conducted an active seismic experiment, in which we found that magnetometers could be used to record seismic rotations. We converted the magnetometer data to rotation-rate data, and validated them by comparing the waveforms and amplitudes with rotation rates recorded by electrokinetic rotation sensors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.