活断層研究
Online ISSN : 2186-5337
Print ISSN : 0918-1024
ISSN-L : 0918-1024
人口減少社会における活断層対策の展望
目黒 公郎大原(吉村) 美保
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ジャーナル フリー

2008 年 2008 巻 28 号 p. 89-94

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Japan entered a longstanding depopulation process in 2006. The total population after 50 years is expected to decrease to about 70% of the current one. In this situation, it is important to avoid social impact due to disasters by guiding population from vulnerable area to safer area. This research focused the risk of active faults among various kinds of natural hazards and studied on the effect of land use control by active fault zoning in Japan.
First, the meaning of land use control along active faults in the society whose population started to decrease was discussed. If the residences in the seismic vulnerable area are relocated to the safer area by the land use control plan, these vacant lands could be effectively used for disaster-prevention facilities. So far, Japan has not adopted the earthquake fault zoning act due to several reasons, while it has been carried out for 30 years in U. S.. However, considering that more lands will become vacant due to depopulation in the future, the possibility of introducing fault zoning act will increase and the discussion on active fault zoning will become more meaningful.
Then, the distribution of population and buildings in the neighborhood of the active faults was analyzed based on GIS databases of the active faults, population and building stocks. The fault zones were hypothetically set along the active faults. In case of the fault zone whose width was decided to be 0.4km referring to the fault zoning act in U. S., the population inside the fault zone was 2.89 million and it corresponded to 2.3% of the total population in Japan. Half of the population living along the faults was located in Kinki area and the effect of land use control was different according to the region. The population inside the fault zone was increased in proportion to the width of the zone.
Finally, the possibility of active fault zoning in Japan was discussed. Based on the obtained results, we think that it is meaningful and possible to adopt active fault zoning in Japan for earthquake damage reduction. However, the appropriate width of fault zones should be discussed considering all the factors such as lessons learnt from past earthquake damage, uncertainty of the traces of both strike-slip and dip-slip fault, social impact of the zones.
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