Abstract
This article is originally based on the author's idea proposed to the present subcommittee, and concluded with reference to the discussion with the subcommittee members. In the beginning, the relationship between landslides and various kinds of their agents are discussed on the basis of ideas of intellectuals proposed on and after 1970's. The fundamental concept of the idea in this discussion, however, rests with Uemura's idea (1974): primary agents arise from action of the circumstantial agents as external causes to the material agents (internal causes). There are many varieties of landslide agents acting over long to short duration or even in an instant. The author believes that the long-middle ones could be primary agents and the short or instant ones inducing agents. There are various kinds of idea including Terzaghi (1950) on those agents and processes leading to landslides, and those ideas are usually not so easy to understand not only for beginners. In this paper, therefore, the author brought these issues to a comprehensive conclusion and tried to show it in some graphic forms.
The united definition of the subcommittee on the primary landslide fell in line as follows: “Primary landslides originate at a point of time when their potential sliding surfaces have almost completely interconnected with each other” and “Any surface and/or undergound deformation or displacement which are the phenomena of initiation of landsliding in advance of primary landslide are defined as precursors of landslide”. These concept of ideas are also shown as a graphic form, and examples of preparatory landsliding and primary landslide are lastly shown in this paper.
