A series of stages in the evolution of slope topography is proposed, and the geomorphic features associated with earthquake-induced landslides in actively uplifting hills of Mio-Pliocene mudstone in Niigata prefecture, central Honshu, are discussed. Four topographic evolution stages are recognized. Linear erosion prominent stage : In this stage, linear erosion, including gully erosion and shallow landslides, is dominant, and few massive erosion events such as deep-seated landslides occur. This stage is seen during the initial uplift stage, which is indicated by hills with a relative relief of less than 100 m. Massive erosion expansion stage : In this stage, both massive erosion and linear erosion occur. Massive erosion prevails when tectonic uplift is active and relief is increasing. This stage is seen during the early to mature uplift stage which is characterized by 100 m to several hundred meters of relative relief. Saturation of massive erosion stage : In this stage, massive erosion affecting whole mountain slopes prevails, but linear erosion continues to occur. Because massive erosion reduces relief, relative relief reaches a steady state between erosion and tectonic uplift, although uplift continues. This stage is seen during the mature uplift stage. Decreasing erosion stage : In this stage, obscure landslide topography is widely distributed, but erosion has decreased as a result of the lessening or end of uplift.

  Landslides induced by the Mid-Niigata Prefecture Earthquake in 2004 were densely distributed in areas of massive erosion expansion stage, where the relative relief was 140 to 240 m.

  For a large number of earthquakes observed by KiK-net (strong earthquake observation network) in mountainous areas, etc., the surface-to-subsurface ratios of Fourier spectra of acceleration amplitudes for seismic waves were obtained, and the average of the ratios for each frequency was used as the average spectral ratio (ASR). The average value of ASR for the period 0.1 to 0.5 seconds is used as the average spectral ratio intensity (ASRI), which is an index of the seismic amplification effect at the observation point. A clear negative correlation was observed between ASRI and average S-wave velocity to a depth of 30m (AVS30). On the other hand, a weak positive correlation was found between ASRI and the curvature of the topographic index. In some cases, the influence of topography on the seismic amplification was suggested. However, there was a group of mountain slopes whose ASR did not differ significantly from that of non-mountain slopes, suggesting that mountain slopes have limited seismic amplification.