Seismic sensing: Comparison of geophones and accelerometers using laboratory and field data

Michael S. Hons

Accelerometers, based on micro-electromechanical systems (MEMS), and geophones are compared in theory, laboratory testing and field data. Both sensors may be considered simple harmonic oscillators. Geophone output is filtered ground velocity and represents its own domain. Modeling shows that geophone and digital accelerometer output is similar in appearance. In laboratory tests, both sensors matched their modeled responses over a wide range of amplitudes. Since the response is accurate in practice, it is used to calculate ground acceleration from geophone output. Comparison of acceleration field data at Violet Grove and Spring Coulee shows most reflection energy is effectively identical from 5 Hz to over 150 Hz. Some consistent differences were noted under strong motion and in the noise floors. In general, when sensor coupling is equivalent, the data quality is equivalent.