3:30 PM - 5:00 PM
[O08-P73] Tachikawa terrace cliff
This study investigated the terrace cliffs around the school from fieldwork and elevation topographic maps.
The terrace topography around the school has now been converted into residential areas, and it is difficult to observe their topographical features on aerial photographs and maps, so the aim was to explore their appearance and topographical changes in detail.
Tachikawa High School is located on the edge of the Tachikawa terrace, as shown in Fig. 1, with the Aoyanagi surface immediately to the south and the present flood plain of the Tama River further south. The boundary with the Tachikawa Plane at the western end of the plane was ambiguous when focusing on the Aoyanagi Plane, so it was investigated during the actual fieldwork. In addition, the differences in the east-west inclination of the Aoyanagi and Tachikawa planes, and the actual topographical displacement of the Aoyanagi plane due to the Tachikawa fault were investigated and analysed based on the literature survey.
As a research method, fieldwork was carried out based on the preliminary literature survey. In addition, a 3D map was created to investigate the topographical features.
In the fieldwork, the red line in Fig. 1 was first assumed to be the Aoyanagi Plane, and fieldwork was conducted at points A, B and C in the map in Fig. 2 (created using a Geographical Survey Institute map) regarding the boundaries between the Aoyanagi Plane, the Tachikawa Plane and the Aoyanagi Plane and the Tama River Lowlands. As a result, it was possible to identify slopes consistent with the map readings in Figure 2. This showed that the area around points A and B, which were particularly narrow, was also part of the Aoyanagi terrace.
Next, in order to make the terrace topography around the school easier to understand, a three-dimensional map was created as shown in Fig. 3 using the Geographical Survey Institute's 3D mapping function. Focusing on the western edge of the Aoyanagi face on this map, it was found that the boundary was indistinct compared to other parts of the terrace cliffs, as shown in Figure 4. The cross-sectional view at straight line αβ in Fig. 3 (Fig. 5) also shows that the western edge has a steeper slope than the other parts of the terrace cliff.
Next, the difference between the east-west slopes of the Aoyanagi and Tachikawa planes, as revealed by the literature survey, was investigated. Figure 6 shows that the Aoyanagi face has a steeper slope than the Tachikawa face. Four cross-sectional maps were set up, A to D in Fig. 7 (D is on the Aoyanagi surface). For the Aoyanagi surface, the inclination was measured separately for the east and west sides of the Yagawa. The results are shown in Figure 8, which shows that the slope of the Aoyanagi surface averaged over the two sections circled in red in D is greater than the slope of the Tachikawa surface averaged over A to C. The changes in the short section measured this time are also shown in Figure X.
Next, a tour of the Yagawa (Photo 4) and the flexural surface of the Tachikawa terrace (Photo 5) at points X and Y in Fig. X was conducted with Haruo Yamazaki. Regarding the large number of stones on the riverbed of the Yagawa River, even though the upper reaches of the river are not mountains, it was found that these stones were transported from between the Aoyanagi and Tachikawa surfaces. The gently dipping fault could be seen on the flexure surface of the Tachikawa Fault.
For future prospects, we would like to graph not only the height of the terrace cliffs between the Aoyanagi and Tachikawa terrace surfaces, but also the height of the terrace cliffs between the Aoyanagi terrace surface and the Tama River lowland, to show more clearly the difference in the east-west directional dip between the Tachikawa and Aoyanagi surfaces. In addition, we would like to print the 3D map using an actual 3D printer to further illustrate the topographical features of the area around our school.
The terrace topography around the school has now been converted into residential areas, and it is difficult to observe their topographical features on aerial photographs and maps, so the aim was to explore their appearance and topographical changes in detail.
Tachikawa High School is located on the edge of the Tachikawa terrace, as shown in Fig. 1, with the Aoyanagi surface immediately to the south and the present flood plain of the Tama River further south. The boundary with the Tachikawa Plane at the western end of the plane was ambiguous when focusing on the Aoyanagi Plane, so it was investigated during the actual fieldwork. In addition, the differences in the east-west inclination of the Aoyanagi and Tachikawa planes, and the actual topographical displacement of the Aoyanagi plane due to the Tachikawa fault were investigated and analysed based on the literature survey.
As a research method, fieldwork was carried out based on the preliminary literature survey. In addition, a 3D map was created to investigate the topographical features.
In the fieldwork, the red line in Fig. 1 was first assumed to be the Aoyanagi Plane, and fieldwork was conducted at points A, B and C in the map in Fig. 2 (created using a Geographical Survey Institute map) regarding the boundaries between the Aoyanagi Plane, the Tachikawa Plane and the Aoyanagi Plane and the Tama River Lowlands. As a result, it was possible to identify slopes consistent with the map readings in Figure 2. This showed that the area around points A and B, which were particularly narrow, was also part of the Aoyanagi terrace.
Next, in order to make the terrace topography around the school easier to understand, a three-dimensional map was created as shown in Fig. 3 using the Geographical Survey Institute's 3D mapping function. Focusing on the western edge of the Aoyanagi face on this map, it was found that the boundary was indistinct compared to other parts of the terrace cliffs, as shown in Figure 4. The cross-sectional view at straight line αβ in Fig. 3 (Fig. 5) also shows that the western edge has a steeper slope than the other parts of the terrace cliff.
Next, the difference between the east-west slopes of the Aoyanagi and Tachikawa planes, as revealed by the literature survey, was investigated. Figure 6 shows that the Aoyanagi face has a steeper slope than the Tachikawa face. Four cross-sectional maps were set up, A to D in Fig. 7 (D is on the Aoyanagi surface). For the Aoyanagi surface, the inclination was measured separately for the east and west sides of the Yagawa. The results are shown in Figure 8, which shows that the slope of the Aoyanagi surface averaged over the two sections circled in red in D is greater than the slope of the Tachikawa surface averaged over A to C. The changes in the short section measured this time are also shown in Figure X.
Next, a tour of the Yagawa (Photo 4) and the flexural surface of the Tachikawa terrace (Photo 5) at points X and Y in Fig. X was conducted with Haruo Yamazaki. Regarding the large number of stones on the riverbed of the Yagawa River, even though the upper reaches of the river are not mountains, it was found that these stones were transported from between the Aoyanagi and Tachikawa surfaces. The gently dipping fault could be seen on the flexure surface of the Tachikawa Fault.
For future prospects, we would like to graph not only the height of the terrace cliffs between the Aoyanagi and Tachikawa terrace surfaces, but also the height of the terrace cliffs between the Aoyanagi terrace surface and the Tama River lowland, to show more clearly the difference in the east-west directional dip between the Tachikawa and Aoyanagi surfaces. In addition, we would like to print the 3D map using an actual 3D printer to further illustrate the topographical features of the area around our school.