The design of ultra‐low‐noise seismic piezoelectric accelerometers (PEs) with integral electronics (IEPE) is presented. They feature probably the lowest noise floor (for their size and weight) and the lowest operating frequencies (near‐dc) ever reported to date among these types of vibration sensors. These highly sensitive sensors can be used for earthquake monitoring and in the earthquake prediction system by detecting and monitoring microseismic fluctuations. The warning system using these sensors would be fundamentally different from current warning systems using the network of hundreds of seismometers across seismically active regions and recording only seismic events. Two Meggitt (OC) IEPE seismic accelerometers, models 86 and 87‐10 having sensitivity of 10 V/G, are described. The model 86 has a weight of about 770 g and a frequency range from 0.003 to 200 Hz at the ±3 dB level. Its noise floor in terms of the equivalent input noise acceleration spectral density is about 37, 7, and 3 nG/ Hz at at frequencies 1, 10, and 100 Hz, respectively. The model 87‐10 is a compact sensor with a weight of about 170 g and a frequency range from 0.02 to 500 Hz at the ±3 dB level. It has noise of about 90, 25, and 10 nG/ Hz at at frequencies 1, 10, and 100 Hz, respectively.
Part of the book: Earthquakes