Development of low cost seismographs for high-density seismic network

Abstract

It is well known that seismic ground motions are affected by intricate subsurface structure and local topography. Due to various local seismic site effects the array of conventional seismic networks is considered insufficient to observe the seismic wave propagation in the local area. Thus, high density measurements are necessary. Furthermore, increasing the density of conventional seismic networks is cost prohibitive due to the installation and maintenance expenses. Therefore, we developed the small, inexpensive and simple seismograph with a wireless seismic network. The simple seismograph uses a microcomputer called ArduinoTM with an accelerometer and real-time clock as the various sensors and 3G shieldTM and ZigBeeTM as communications. It observes acceleration and computes the maximum of a three-component waveform in arbitrary periods, and transmits data through the communication system. Since a 10-Hz low pass filter is applied, it is also possible to simply calculate the instrumental seismic intensity. We conducted a series of comparative experiments and confirmed that the measurement is of high accuracy. Moreover, we succeeded in power saving by performing data transmission using 3G wireless communication only when the strong ground motion had been detected. A high density ground acceleration imaging system will can be constructed using the simple seismograph and the local site effect on strong ground motions will be determined.