Active nappe with a high slip rate: Seismic and gravity profiling across the southern part of the Itoigawa-Shizuoka Tectonic Line, central Japan

Uplift and denudation history of the Akaishi Range, a thrust block formed by arc‐arc collision in central Japan: Insights from low‐temperature thermochronometry and thermokinematic modeling

“…Consequently, three combinations shown in Figures c1, c2, and c7 and c8, i.e., Z d = 20–22.5 km, tan θ = 1/1.5–1/1( θ = 34–45°), and V = 5–7.5 mm/yr, best explain the data. These values are consistent with previous estimates, i.e., fault dip of 35°–40° obtained by seismic array observation [ Panayotopoulos et al ., ] and dip‐slip rate of 3–11 mm/yr along the frontal thrust [ Hirakawa et al ., ; Kumamoto and Ikeda , ; Ikeda et al ., ] assuming a thrust‐front migration [ Ikeda , ] from the boundary thrust to the frontal thrust [ Tajikara , ]. Based on simple trigonometric calculations and using the slip rates and fault dips, the bedrock uplift rates are estimated at ~4 mm/yr for the three best cases ( V H in Table ).…”

“…The southern part of the ISTL-FZ is composed of west dipping reverse faults [e.g., The Research Group for Active Faults of Japan, 1991]. The dip of the frontal thrust is generally as low as~15°near the surface [e.g., Kumamoto and Ikeda, 1993;Ikeda et al, 2009], whereas that of the boundary thrust is steeper [e.g., Ikeda et al, 2009]. The frontal and boundary thrusts are considered to sole into a single thrust fault at depth [e.g., Ikeda et al, 2009].…”

“…The dip of the frontal thrust is generally as low as~15°near the surface [e.g., Kumamoto and Ikeda, 1993;Ikeda et al, 2009], whereas that of the boundary thrust is steeper [e.g., Ikeda et al, 2009]. The frontal and boundary thrusts are considered to sole into a single thrust fault at depth [e.g., Ikeda et al, 2009]. Considerably high dip-slip rates of 3-11 mm/yr during the late Quaternary were estimated for the frontal thrust on the basis of the deformation of fluvial terraces [Hirakawa et al, 1989;Ikeda et al, 2009] as well as the subsurface structure obtained by seismic reflection [Ikeda et al, 2009] and gravity surveys [Kumamoto and Ikeda, 1993;Ikeda et al, 2009].…”

“…The frontal and boundary thrusts are considered to sole into a single thrust fault at depth [e.g., Ikeda et al, 2009]. Considerably high dip-slip rates of 3-11 mm/yr during the late Quaternary were estimated for the frontal thrust on the basis of the deformation of fluvial terraces [Hirakawa et al, 1989;Ikeda et al, 2009] as well as the subsurface structure obtained by seismic reflection [Ikeda et al, 2009] and gravity surveys [Kumamoto and Ikeda, 1993;Ikeda et al, 2009]. On the other hand, dip-slip rates along the boundary thrust are smaller.…”

Crustal structure in the northwestern part of the Izu collision zone in central Japan

“…In this scenario, reverse faulting along the northernmost collisional boundary (SHF), located at the southern end of the Kofu Basin, is likely to have produced the fore-arc basin between the arc and outer-arc rise. Drilling data and seismic reflection profiles in the Kofu Basin indicate that basin fill sediments thicken toward the southwest (Yamanashi Prefectural Government 2002), suggesting that reverse faulting along the SIF at the Western end of the Kofu Basin also contributed toward the formation of the basin (Ikeda et al 2009). …”