Suitability of Low-Cost Three-Axis MEMS Accelerometers in Strong-Motion Seismology: Tests on the LIS331DLH (iPhone) Accelerometer

At the present time, micro-electro-mechanical system (MEMS) accelerometers seem to provide adequate sensitivity, noise level, and dynamic range to be applicable to earthquake strong-motion acquisition. The current common use of MEMS accelerometers in the modern mobile phone may provide a new means to easily enormously increase the number of observations when a strong earthquake occurs. However, before utilizing the signals recorded by a device, like a mobile phone equipped with a low-cost three-axis MEMS accelerometer for any scientific purpose, it is important to verify that the signal collected provides reliable records of ground motion. In this paper, we have tested the LIS331DLH MEMS accelerometer installed in the iPhone mobile phone using a vibrating table and the EpiSensor FBA (force-balance accelerometer) ES-T as the reference sensor. Our tests show that, in the typical frequency and amplitude range of interest of earthquake engineering (0.2-20 Hz and 10-2000 mg, in which g is the standard gravity of acceleration, or 9.80665 m/s(2)), the LIS331DLH MEMS accelerometer has excellent frequency and phase response, comparable with that of some standard FBAs produced for strong-motion seismology. The main drawback of the LIS331DLH MEMS accelerometer is its low sensitivity, due to the high level of instrumental self noise, and so it can be used effectively only to record moderate to strong earthquakes (M-L > 5) near the epicentral area.