Rotational Seismology with a Quartz Rotation Sensor

Abstract

We describe the construction and performance of a new high-precision ground- or platform-rotation sensor called the Quartz Rotation Sensor (QRS). The QRS is a mechanical angular accelerometer that senses rotational torque with an inherently digital, load-sensitive resonant quartz crystal. The noise floor is measured to be ∼45 pico-radians/root (Hz) near 1 Hz, and the resonant period of the sensor is about 10 s, making it a broadband sensor. Among similarly sized broadband rotation sensors, this represents more than two orders of magnitude improvement in noise floor near 0.1 Hz. We present measurements of rotational components of teleseismic waves recorded with the sensor at a vault. The QRS is useful for rotational seismology and for improving low-frequency seismic isolation in demanding applications such as the Laser Interferometer Gravitational-Wave Observatories.

A vacuum-compatible cylindrical inertial rotation sensor with picoradian sensitivity

“…3 Multiple devices now reach this sensitivity including ring-laser gyros [4][5][6] and flexure-based inertial rotation sensors. [7][8][9] Many of these devices are large (meter-scale) and must be maintained with human intervention, making them inadequate for certain applications. Specifically, to operate a sensor within the seismic isolation systems of gravitational wave observatories, the sensor must be ultra-high vacuum compatible and remotely operable.…”