Active faults and principal tectonical lineaments in Kanto plain and its surrounding area
1977 Volume 86 Issue 2 Pages 92-109
Details
1977 Volume 86 Issue 2 Pages 92-109
The purpose of this study is to obtain the fundamental data for the inland earthquake in the upper part of the crust and for the reasonable landuse plan in Tokyo Metropolitan District. This study was carried out by air-photo-interpretation and field observation.
In the photo-interpretation, attention was paid to the geomorphological peculiarity such as systematical pattern of lineaments, difference of height and inclination between both side of the fault line, shutter ridge and off-set valley, mound and trench, sag pond and its burried type, terminal facet, kerncol, fault scarplet, etc. Active faults were recognized from the facts that terraces and alluvial landforms along the fault lines are deformed by fault action, or fault planes are observed in the Quaternary bed.
The result of the photo-interpretation and the field observation is compiled of Fig. 1, in which the thick lines mean the active faults and the others are the faults not yet recongnized as the active ones. The active faults which were newly found by the authors are as follows :
Length Strike Vertical disp.(down) Horizontal disp.
1. TACHIKAWA F. 32km N 40°W SW left (?)
2. OGOSE F. 16km N 25°W E -
3. ENAMI F. 10km N 33°W SW -
4. ISOBE F. 5km N 35°W SW -
5. OKUBO F: 7km N 70°W SW -
6. KAJIYADO F. 5km N 50°W SW left
7. KOTESASHI F. 20km N 57°E N -
8. AGAKUNI F. 14km N 90°E N right
9. TAKAMINE F. 5km N 51°E SE -
Of above active faults, the some parts of fault plane were observed geologically at several outcrops along TACHIKAWA F. (Photo 1, 2), OGOSE F. and OKUBO F. (Photo 6). Besides, the authors also observed the fault planes along FUKAYA F. (Photo 3, 4) and HIRAI F. (Photo 5), which had been already reported as the active faults by T. Matsuda from the geomorphological points in 1975. These newly observed faults are almost all reverse fault or thrust.
The synoptical distribution pattern of the tectonical lineaments in Kanto Plain and its surrounding area is as seen from Fig. 10. From this pattern, the authors can note that the NW-SE line system composed of KOZU-MATSUDA-KAWAHARABATA LINE, TSURUKAWA-ISEHARA LINE, TACHIKAWA AND ITS EXTENDED LINE, FUJIOKA-ARAKAWA LINE and KIRIU-AGATSUMA LINE is remarkable in their continuity and parallel. On the other hand, other? line systems do not show so regularlly as NW-SE line system. However, SHIBUSAWA-SURUGAOYAMA LINE, TOMIOKA SOUTH LINE and ASHIO FAULT LINE of E-W or NE-SW line system is remarkable in length and continuity.
The authors have plan to survey the tectonical lineaments in detail which have not yet recongnized as active fault, and to study various characters of active fault such as the total length, the active cycle, the average displacement and the stress system in Kanto District.
