[S-SS12] Seismic wave propagation: Theory and Application

[SSS12-P06] Repeated noises of 7-15 second interval in the seismograms recorded at the seashore landslide

*Issei Doi¹, Sumio Matsuura¹, Hikaru Osawa³, Tatsuya Shibasaki², Shinichi Tosa² (1.Disaster Prevention Research Institute, Kyoto University, Japan, 2.Japan Conservation Co. Ltd., 3.Mountain Science Center, University of Tsukuba, Japan)

In recent days, seismic noises are used to estimate subsurface structure and to detect its temporal changes in the methods such as seismic interferometry. It is important to know the characteristics and the generation mechanisms of seismic noises in order to precisely interpret the results for natural phenomena.

We used the seismic data recorded at the station on the seashore landslide in southeastern Hokkaido, Japan. In the seismograms, repeated noises of 7-15 second interval were intermittently found. In order to know the generation mechanisms of these repeated noises, we firstly tried to automatically detect them as follows. 1) We calculated the three-dimensionally synthesized waveform with the length of one hour. 2) We calculated the average of the amplitude of synthesized waveform every one second and obtained its distribution. 3) Fitting the distribution to Gumbel one, we recognized the repeated noise occurence for the waveform with the scale parameter larger than 0.2 empirically. Comparing the timing of the repeated noise occurence and the tide height, it was found that the repeated noises were found mainly at high tide.