A MEMS Based Electrochemical Vibration Sensor for Seismic Motion Monitoring

This paper presents a micro-electro-mechanical system (MEMS) based electrochemical vibration sensor for seismic detection. Simulations were conducted to analyze the effect of the insulating spacers thickness on the sensitivity of the devices. Then, devices with different insulating spacers thicknesses were fabricated based on MEMS processes. The devices sensitivity was confirmed by a customized experimental platform, verifying the simulation results. In addition, the device performance was characterized with a quantified bandwidth of 0.2–5 Hz with sensitivity of 30.2 V/
$({\rm m}/{\rm s}^{2})$
and a linear voltage output as a function of the input vibration amplitude (up to 10 mg). The devices noise was determined as
${-}{\rm 140}~{\rm dB}$
at 1 Hz. A random-vibration testing in the laboratory environment was conducted, where response correlations among seven devices were calculated as
$0.976\pm 0.017$
, suggesting high device repeatability. A field test was conducted right above a subway line to detect the seismic motion caused by the train and test results showed that the performance of the proposed devices was comparable with that of the commercial product MET-1001. A field test was also conducted in a prairie to monitor natural seismic motions and experimental results indicated that the proposed electrochemical sensors can detect seismic motions in a lower frequency domain with an energy peak at around 0.3 Hz compared with conventional moving-coil seismic sensors with an energy peak at 3 Hz. This newly proposed vibration sensor may function as a promising seismic motion detecting device in the field of geophysical prospecting where low-frequency seismic motion detection is requested.
$\hfill[2013{\hbox{-}}0208]$