Subsurface geometry and structural evolution of the eastern margin fault zone of the Yokote basin based on seismic reflection data, northeast Japan

High-resolution seismic reflection profiles across coseismic fault scarps reactivated during the A.D. 1896 Rikuu earthquake along the eastern margin fault zone of the Yokote basin (EFZYB) in northeast Japan, correlated with borehole stratigraphy and geologic mapping, provide insights into its detailed kinematic history and structural evolution. In spite of along-strike variations of thrust geometries both at ground surface and at shallow depth, the EFZYB has commonly formed as forward breaking imbricate thrust systems. Near surface complexity of thrust geometries appears strongly affected by mechanical decoupling between layers within middle to late Miocene mudstone. Cross-section balancing across the Mahiru Mountains shows strong correlation of the millennial uplift rates with mountain topography but its weak correlation with the late Pleistocene uplift rates. Considering the thrust trajectories estimated by the balanced cross sections, the millennial dip-slip rate are consistent with the late Pleistocene dip-slip rate, suggesting that the EFZYB has accumulated strains at a constant rate since the onset of its fault activity.