Earthquake Data Recorded by the MEMS Accelerometer: Field Testing in Idaho

The Idaho National Engineering and Environmental Laboratory (INEEL) operates 26 seismic stations remotely located in southeastern Idaho and 25 strong-motion accelerographs located at critical facilities at the INEEL site. The INEEL seismic network has recently upgraded standard analog instrumentation at all of its seismic stations to digital recording systems. Seismic data are transmitted to a central recording laboratory in Idaho Falls, Idaho using 900 MHz wireless modems. INEEL has also chosen digital recording systems to replace the 25 analog film-recording strong-motion accelerographs. INEEL chose to field-test the Applied MEMS, Inc. model SF1500A tri-axial accelerometer1 with the digital recording system for suitability in earthquake ground-motion recording. In this note we report on the results of our field tests. MEMS (Micro ElectroMechanical Systems) sensors are miniature sensors made in wafer fabrication facilities similar to semiconductor foundries. Many types of commercial MEMS accelerometers exist and are used for a wide range of applications such as air bag systems, detecting industrial vibrations, and strong-motion recording. The Applied MEMS, Inc. model SF1500A is an analog force-feedback accelerometer featuring a variable capacitance, silicon bulk-micromachined acceleration sensor, and a custom low-power mixed-signal integrated circuit. The custom design results in a very lownoise, low-distortion sensor with high bandwidth, dynamic range, stability, and robustness (Figure 1). The SF1500A accelerometer can withstand shock impacts up to 1,500 g and has a demonstrated operating temperature range from –40°C to +85°C. The nominal bandwidth is from DC to 1.5 kHz with a …