The western marginal active fault zone (Nishine faults group) of Shizukuishi basin, northeast Japan, were precisely mapped in detail. Their late Quarternary activity were reexamined, with implication to the surface fault of 1998 earthquake having occurred below this basin. Four faults named Fl, F2, F3 and F4 trending N-S have at most vertical slip rate of 0.5mm/yr. The F2 fault is the longest, ca. 13km, and have mainly contributed the differentiation of the basin from mountains. The Fl fault and 1998 coseismic surface fault are possibly a branch from the F2 fault. As fault movement at the 1998 earthquake was limited with a little of 40cm in vertical slip, the Nishine faults group still has some potential that large earthquake occur accompanied by their activation in future.
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