Scouring is a disaster that threatens safe driving of trains. So, we proceed with the development of a new scour detection device is also possible state grasp of before scouring inclined. The natural frequency of the pier is calculated from the measured waveform, and when the value drops, it is judged as scoured state. In order to verify whether the natural frequency can be calculated stably from the constant microtremors, long-term microtremors measurement was carried out. From the calculation results, we verified the long-term stability of the natural frequency calculation and analyzed the natural frequency fluctuation tendency when the water level increased. It was found that the natural frequency can be calculated stably and accurately in daily water level fluctuations where disasters do not occur.
