観測地震波スペクトルを用いた地震動の周期特性が土砂移動に及ぼす影響に関する事例研究

抄録

Even if seismic intensity or peak ground acceleration (PGA) is close to that of past earthquakes which caused catastrophic sediment disasters, some earthquakes have few coseismic landslides. In order to clarify the reason for this, we compared the spectra of earthquakes with numerous landslides (NLE) and earthquakes with few landslides (FLE) and discussed the influence of periodic characteristics of seismic motion on coseismic landslide occurrences. The compared spectra were Fourier spectra, acceleration response spectra, and velocity response spectra. We compared a series of spectra from short to long period between NLE and FLE, considering distance from the fault/hypocenter, seismic intensity and PGA. As a result, in the short-period component, the spectra of NLE and FLE generally overlapped, making the difference between NLE and FLE unclear. On the other hand, the difference tended to be significant in long-period components, as the NLE spectra exceeded the FLE spectra at periods longer than 1 second. Based on these results, we suggest that it is possible to improve the accuracy of judging the number of coseismic landslides by considering the long-period components of spectra in addition to the seismic intensity and PGA.