Internal Structure of the Primary Landslide on the Amaze Anticline

Abstract

The Primary landslides have left the scars approximately 2.8 Km width, at the central part of the Amaze anticline, Niigata Prefecture. The lower part of slide area has denudated from marine erosion, consequently the internal structure resulting from rockslides are observable on the sea bottom near the coast. The aid of aerial photographs may be effective in identifications.
The strata are distorted, brecciated, forming a chaotic mixture of irregular blocks, among which folded structures are included. The strike of strata separated from one another by fractures, are oriented at random, but it persists a stratification on independent block.
Furthermore, field and air-photograph investigations revealed that these pecuriar structures, which are characterized by a mozaic pattern with the folded structures, are confined to the zones encircled by the.scarps of rockslides, indicating that they have formed under the influence of gravity. The mechanism of folded structures are best accounted by compressive force derived from gravity-induced movement towards the sea. The rockslides may be occurred by being strongly controlled by the tectonic fractures.