[S-SS34_29PO1] Active faults and paleoseismology

[SSS34-P07] Geologic structures around the coastal area of the southern part of the active eastern boundary fault zone of Ishikari l

*Tomoyuki SATO¹, Taku KOMATSUBARA¹, Yoshihide KOU¹ (1.Institute of Geology and Geoinformation, Geological Survey of Japan, AIST)

Keywords:Active eastern boundary fault zone of Ishikari lowland, Seismic survey, Quaternary, Hokkaido, Coastal area

A 130-km-long N-S trending active fold and thrust zone (eastern boundary fault zone of Ishikari lowland) occurs in the Ishikari lowland and off the Yufutsu plain. This fault system is one of the boundary faults between the Kuril arc and the Northeast Japan arc. We surveyed around the coastal area of the Yufutsu plain based on the marine high-resolution seismic-survey and the database of land borehole cores. As a result, two active anticlines (Yufutsu anticline and Hamaatsuma anticline) were recognized. These anticlines can be correlated to the anticlines described as a part of the active eastern boundary fault zone of Ishikari lowland (AIST, 2007). The trand of the Yufutsu anticline was N-S despite The Headquarters for Earthquake Research Promotion reported the trend was NW-SE. The Hamaatsuma anticline continued to the Mukawaoki anticline and the southern end of the fault zone extend to the southern end of the Mukawaoki fault which is concerned to the Mukawaoki anticline.AIST(2007)Activity survey of the eastern boundary fault zone of Ishikari lowland. Working papers. H18-8, 35p.Headquarters for Earthquake Research Promotion(2010) Evaluation of the eastern boundary fault zone of Ishikari lowland (revised). 34p.