5:15 PM - 6:30 PM
[SSS31-P17] Holocene activity of the Northern Marginal Faults of the Saga Plain
Keywords:Northern Marginal Faults of the Saga Plain, normal fault, large-scale geographical map, tectonic bulge, average vertical slip rate
F3 faults correspond to the active fault that has been pointed out in Research Group for Active Tectonic Structures in Kyushu ed. (1989) and Nakata-Imaizumi ed. (2002). The F3 faults were recognized as distinct scarps of about 1.8m on alluvial fan surface (L1 planes). These faults were intermittently until Jobaru-river from Saga City Yamato-cho, but could be clearly tracked. The average vertical slip rate of F3 faults in L1 planes were estimated to 0.07mm/yr. F6 faults could be tracked continuously lineament from the Kase-river to the Jobaru-river on L2 surfaces. F6 faults has tectonic bulge that may be low fault scarps or about 50cm low fault scarps on the L2 planes. These were observed the slopes of the terrace surfaces by field observations and topographic profile. The average vertical slip rate of F6 fault in L2 planes were estimated to 0.07mm/yr. F7 faults were located on the south side of the F6 faults. F7 faults could be tracked continuously from the Kase-river to the Jobaru-river on L2 planes. In Saga-city Kuboizumi-cho Shimoizumi, we made simple boring survey in the hanging wall and footwall side of the border the F7 faults. As a result, AT was confirmed in the deposits of L1 planes that were buried terraces. F7 faults of average vertical slip rate were estimated to be at least 185cm or more. Thus, average vertical slip rate of F7 faults were estimated to 0.07mm/yr.
Tectonic geomorphology that were estimated to scarps that were observed continuously on the L2 planes of the North portion of the Saga plain. Because of texture on the L2 surfaces were observed, Holocene activity of this fault zone was active at least once after L2 planes formation (7.3ka). L3 planes were observed scarps about 50cm, but it's issues there were also the possibility of artificial modification.