2010 Volume 48 Issue 2 Pages 1-10
In this study, we investigated on a mapping method by GIS for the estimated JMA (Japan Metrological Agency) seismic intensity of the 2005 West off Fukuoka Earthquake at March 20, 2005. A questionnaire intensity survey on the earthquake damage was carried out for the mapping. The estimated intensity, in other words the values of the estimated seismic intensity were calculated by about 2500 questionnaires that had been answered by the students and teachers of some universities in Fukuoka Prefecture. The items of questionnaires are attributes such as locations where a respondent experienced the earthquake, age, sex, landform and ground condition, objective degree of ground motion on buildings, furniture etc., and subjective degree of ground motion on feelings such as surprise and fear. We calculated the estimated intensity from the answers of the questionnaires by Excel, and compiled the estimated seismic intensity maps on the northern Kyushu area and the Fukuoka urbanized area by the kriging method of GIS. We clarified the geomorphologic and geologic conditions related to the earthquake damage using the maps and discussed the accuracy and usefulness of the maps by comparing the estimated intensity with the measured seismic intensity at the observation points.
We concluded the followings through the study.
1) In the northern Kyushu area, the estimated intensity was large at the adjacent area of epicenter, plain, and the boundary area between mountains and plains. On the other hand, it was small at the far side of the mountains from the epicenter.
2) In the Fukuoka urbanized area, the intensity was large at the alluvial plain, the reclaimed land, the marginal area of hill and the northern foot of Sefuri Mountains. On the other hand, it was small at the mountain, the hill and the terrace.
3) The estimated intensity by the kriging method of GIS is in general agreement with the measured seismic intensity. The estimated intensity map by that method is not good enough for showing the realistic distribution of the measured seismic intensity, as compared with the map by the IDW method. But the kriging method can be useful for compiling an estimated seismic intensity map by adjusting the number of using data in GIS calculation.
4) The validity of discussion on the relationships between the geomorphologic and geologic condition and earthquake damages is guaranteed in the estimated seismic intensity map.
5) We need to pay attention to the impartiality on the attributes such as age and sex on the respondents for GIS mapping accurately when the questionnaire intensity survey is done.
