Development of Seismic Intensity Meters Equipped with MEMS Acceleration Sensors

Abstract

After the 1995 Hyogo-ken Nanbu Earthquake, a strong-motion seismograph network has expanded exponentially in Japan. A strong-motion seismograph, including a seismic intensity meter, has four main parts: the sensor module, the analog-to-digital data conversion module, the computation module, and the communications module, which have all been improved as technology advances. In contrast with the rapid technological development, miniaturization, and price reduction of AD conversion, computation, and communications modules, the sensors have been utilizing servo type accelerometers to convert seismic motion into electric signal, and have not shown significant technological change and particularly price reduction from earlier iterations. Modern acceleration and impact sensor modules, which are often installed on smartphones and cars, are called MEMS (Micro Electro Mechanical Systems). These are devices that integrate mechanical elements and electronic circuits made through the help of microfabrication technology. While MEMS is ultra-small, low-cost and able to measure in a wide range, its resolution is low and could barely be used for seismic observation to measure approx. 1×10^-2 m/s² vibration. However, recently, extremely low-noise MEMS acceleration sensors that can be used for strong-motion seismographs have been developed and sold. We developed a MEMS type seismic intensity meter adapting the MEMS acceleration sensor, and evaluated it with wireless data transfer in EPS rooms and basement floors of high-rise buildings.