墓石の転倒からみた兵庫県南部地震の被害分布とその地形環境 Distribution of the Damage Caused by the Earthquake of Jan. 17, 1995 and Its Geomorphic Environment as Seen from Fallen Tombstone
On Jan. 17, 1995, the Southern Hyogo Prefecture Earthquake struck Kobe, including the surrounding cities. We surveyed the extent of the damage brought about by this earthquake upon tombstones. We then made a geomorphological classification in order to examine the relation between landform types and the results of the survey.<br> We surveyed a total of about 46, 000 tombstones distributed among 441 cemeteries in the Hanshin area and the northern part of Awaji island (Fig. 1). A certain kind of tombstone, made up of three or four stones arranged in steps, was selected for this survey. Our survey was conducted to find out what percentage of this type of tombstone in each cemetery had had its upper level toppled over by the earthquake (hereafter known as PFt).<br> The distribution of PFt is shown in Fig. 2. High PFt zones (zones registering 60% PFt or more) were located in the area between the northwestern part of Awaji island and the southern foot of the Rokko range and in Takarazuka city. In contrast, areas including the northeastern part of Awaji island registered low values of PFt.<br> The following are areas registering highest PFt;<br> (1) The northwestern part of Awaji island. High PFt zones were located mostly on alluvial lowland (Fig. 3). Hills and terraces only indicate 20 40% PFt, even those located less than 200m from the Nojima earthquake fault (Fig. 4).<br> (2) In the Akashi area, cliffs, , including the nearby areas, show 60% PFt or more, while terrace sur faces show lower PFt (Fig. 5). With regards to alluvial plain, PFt value seems to decrease for areas farther inland, except for location on old river channel.<br> (3) At the southern foot of Rokko range, except in artificially altered land, PFt is mostly under 10% in the mountain and hill areas (Fig. 6). Highest PFt values can be observed in present fan and backmarsh, averaging 83% and 70%, respectively. Sandbar and beach ridge registered lower PFt to a certain extent. Also, newer formations registered higher PFt (Fig. 7).<br> (4) Around the Itami terrace, two areas showed PFt of 60% or more (Fig. 8). One is on the alluvial plain beside the Muko river, the other is at the foothill in the northern Takarazuka city. These distri butions correlate with the active fault (F-'F) and the Arima-Takatsuki tectonic line. It was also found that backmarshes indicate 10-30% PFt, which is slightly higher than the surrounding alluvi al plain.<br> In conclusion, the examples above show that PFt was mainly determined by each location's landform type, even for areas near the earthquake fault. We think that PFt reflects the ground character of the landform, considering the fact that high PFt values were observed on areas with soft ground foundation such as alluvial plain, present fan, and backmarsh. With regards to the planning of earthquake damage prevention measures, it is therefore important to take into account data on ground foundations as well as classifications.
- 地理学評論. Ser. A
地理学評論. Ser. A 69(1), 39-50, 1996-01