Abstract

The newly developed low-cost micro-electro-mechanical system (MEMS)-based acceleration sensors exhibit sufficient accuracy and stability to monitor the shaking of structures caused by an earthquake. We have developed a practical shaking-monitoring system using MEMS-based acceleration sensors and a 920 MHz multi-hop radio communication method that offers reliable radio wave communication, even within buildings. In this system, the base clock of each sensor unit must be closely synchronized to the master clock to minimize acceleration-induced phase synchronization error. In the proposed system, this error can be limited to three milliseconds in a system of multiple sensor units.