The Japan archipelago is a part of the Circum Pacific Orogenic Belt
and is geologically very unstable. The bedrock materials which comprise
the mountain terrain have been severely fractured since its formation and
have developed numerous fault fracture zones. The Japanese archipelago
is often referred to as "scar-laden islands". The mountain region
displays a wide variety of topography with steep terrain that often exhibits
a stage of maturity. Furthermoure, the islands are located within the monsoon
zone and receive abundant rainfall. Coupled with early summer rainy spells
and later typhoons, numerous landslides occur resulting in staggering damages.
Since 1960, Japan has experienced a high level of land utilization
as part of the national polity. In particular, residential developments
near and around large cities, reclamation of coastal regions, and construction
of dams and highways have all severely altered the existing topography
(which is one of the major contributing factors that cause landslides).
Due in part to this relationship, citizens in general have a keen sense
of awareness concerning landslide disasters.
There fore, when a catastrophic diasater should occur around us, we
try to understand the cause and effet relationship between the physical
conditions and the type and nature of the disaster. Recent large scale
disasters include: numerous debris flows in Nagasaki City and the surrounding
region caused by the concentrated extremely heavy reinfall of July, 1982;
the Jizuki-Yama Landslide of Nagono City of July, 1985; and the widespread
disaster caused by the Hyogo Earthquake of January, 1995. All of these
disasters claimed and affected many lives, and have demonstrated a close
relationship between natural disasters and the lives of citizens living
in the affected regions. The above incidents have also acted as a "wake-up"
call for us to be aware of the urban types of disasters which have resulted
in new problems.
In order to reduce the affects of natural disasters in the 21st century,
the United Nations established the "International Decade of Natural
Disaster Reduction" in 1990 (in which the decade is nearly one-half
over). During the international conference held at Yokohama in 1994, the
following objectives were adopted: 1) to increase the awareness of disaster
prevention on an international level; and 2) to build up the regional mutual
cooperation structure. Furthermore, it is important to realize that every
effort is required in order to reduce the natural disaster, and to take
a step forward to try to predict disasters.
Since establishment of the Japan Landslide Society in 1963, 34 annual
meetins and numerous symposiums have been organized and over 120 issues
of the journal "Landslides" have been published. Recently, the
society published the annual newsletter "Landslide News" in English,
and is distributed overseas and received well. The 5th revision of "Landslides
in Japan" focuses on the current understanding of landslide origin,
and discusses some of the problems concerning landslide investigations
and research in Japan. It is our desire that this pubication will be distributed
not only among the professionals involved with landslide research and landslide
mitigation, but also among the general public to increase public awareness
and development of technology regarding disaster prevention. We sincerely
hope that these efforts will contribute to the reduction of the damages.
Saburo Nakamura
President, The Japan Landslide Society
