Wide-Band Vertical Superconducting Accelerometer for Simultaneous Observations of Temporal Gravity and Ambient 

Seismic Noise

   Dong Ma , Xikai Liu, Mao Zhang, Ning Zhang,† Liang Chen, and Xiangdong Liu*

Ambient seismic noise contains valuable information about the structural properties of Earth’s subsurface. The superconducting gravimeter (SG) is the most suitable instrument for temporal gravity, but not for microseisms due to its limited bandwidth. We report an alternative type of vertical superconducting accelerometer with a bandwidth as high as 0.7 Hz. Its sensitivity is comparable with the current SG. The accelerometer consists of a superconducting mass-spring oscillator and a displacement sensor based on a superconducting quantum interference device. The oscillator is constructed by levitating a Meisnner-state proof mass using combined positive-stiffness and negative-stiffness superconducting coils. Its natural frequency can be adjusted by the coil currents over a large range. The enhanced sensitivity of displacement sensing compensates the sensitivity loss imposed by the broadened bandwidth. Experimental tests show that both the gravity variation and the microseism can be extracted from the measurement data. It would be quite meaningful to monitor the temporal gravity and structural evolution using such an accelerometer array in sensitive zones, for example, the crustal fault and volcano zones.

DOI: 10.1103/PhysRevApplied.12.044050