京都盆地南部の旧巨椋池周辺に認められる変動地形と伏見湊の普請

Tectonic Geomorphology in the Southeastern Part of the Kyoto Basin and the Fushimi Harbor Constructed by Hideyoshi Toyotomi in the Azuchi-Momoyama Period

GOTO Hideaki

内海文化研究紀要

Bulletin of the Institute for the Cultural Studies of the Seto Inland Sea

[PISSN] 0386-3182

[NCID] AN00176886

The Kyoto basin developed as a tectonic basin and is divided into north and south by the Ujigawa fault, an E-W trending active fault. The northern basin is bound by active faults distributed along the west and east sides. The paleo-Oguraike pond, a large round pond with a diameter of approximately 3 km, was located in the most northern portion of the southern basin. It was reclaimed in the 1930s because of a shallow and poorly drained pond. Tectonic geomorphology around the paleo-Oguraike pond and the cause of its formation is not known, except for the existence of the Ujigawa fault. Thus, the author examined the tectonic geomorphology around the eastern margin of the paleo-Oguraike pond, based on a detailed digital elevation model (DEM), processed from light detection and ranging measurement (LiDAR) data, which was provided by a 5 m-mesh DEM from the Geospatial Authority of Japan.
Consequently, the flexure scarps on the terraces were newly identified along the western margin of the Uji hills located to the southeast of the paleo-Oguraike pond and named the Uji fault. Around the southeastern margin of the paleo-Oguraike pond, narrow terraces with a width of approximately 300 m, distributed north to south, are tilted to the west between the Ujigawa river and the paleo-Oguraike pond. It is estimated to have been deformed by the active fault along the eastern margin of the pond because of the northern extension of the flexure scarps of the Uji fault.
Moreover, the active fault would have extended along the eastern margin of the pond because the alluvial plains of the Ujigawa river were not concordant with the theoretical feature. The slightly elevated area and islands appear to be distributed only in the eastern and northeastern side of the paleo-Oguraike pond based on analysis of the present topography and the Jori remains of paddy field and maps.
The Fushimi harbor was constructed on the large, elevated area formed by the active faults of the Ujigawa, Momoyama, and Hanayama-Kanshuji faults by Taiko Hideyoshi Toyotomi, the father of the Imperial adviser, in the Azuchi-Momoyama period. The harbor was separated from the paleo-Oguraike pond to form the Makishima-Tsutsumi embankment along the Ujigawa river and Taiko-Tsutsumi along the east side of the pond. These embankments enclosed a slightly elevated area, which was probably formed by the active fault on the eastern side of the pond. Consequently, large ships had safe access from Osaka or the Seto inland sea to Fushimi, the outer port of Kyoto, the largest city at that time.

jpn

広島大学文学部附属内海文化研究施設

Copyright (c) 2022 by Author

[ISSN] 0386-3182

[NCID] AN00176886