抄録
In this paper we enforce the estimation of seismic damage from a new view-point of considering temporal and spatial growth of a region. It is quite natural that the risk potential inherent to a region, i.e., the potential loss of an earthquake receiver side, such as seismic resistivity of builbings and their distribution pattern, should be gradually changing in the longer term of several decades. This is due to such facts as the increasing diversity of modern buildings and the expansion of residential areas in some large cities over the surrounding land. Most of the past studies are insufficient in a point that the probable damages in a region were estimated in no much attention to such changeability of risk potential. This paper introduces a case study for long term estimation of the seismic risk in an expanding urban area of Sapporo Region, Japan. First, the seismic intensity distribution in Sapporo Region is estimated for the presumed earthquake which might occur at Ishikari Bay near this region. Then, the probable damage of dwelling houses is estimated for occurrence at any time during the next 50 years considering the time-dependent growth of the urban area. The urbanized Sapporo area has rapidly been growing toward the presumed source region and the projected areas for new suburbia are sited on soft soil deposits of peat and clayey silt etc., which correspond to the high intensity zones for the Ishikari Bay earthquake. Therefore, considering the future growth of urban area, the estimated damage rate of residential buildings would be doubled after 50 years. This tells the definite importance of long term land use planning, especially in urban and vicinity area, in consideration of the time dependency of risk potential in the receiver side as well as seismic activities influencing the region.
