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Progress in Earth and Planetary Science
Fig. 6 | Progress in Earth and Planetary Science

Fig. 6

From: The nature of the Pacific plate as subduction inputs to the northeastern Japan arc and its implication for subduction zone processes

Fig. 6

a Thickness of sediment in two-way traveltimes determined by MCS surveys (Fujiのはe et al. 2020). Red circles show petit-spot cluster sites where many small and young volcanoes are observed (Hirano et al. 2006). Petit-spot sites A and C are located at the areas of thin-sediment cover. b Distribution of chert unit along survey lines (red) and coseismic slip distribution of the 2011 Tohoku earthquake determined by geodetic study (black contour lines and gray shaded area) (Iinuma et al. 2012). Yellow circles represent the area of petit-spot clusters (e.g., Hirano et al. 2006; Hirano 2011), which corresponds to the area of missing chert (Fujie et al. 2020). Yellow squares represent tremors determined by S-net seafloor observatories (Nishikawa et al. 2019). c Schematic diagram of the sedimentary structure proposed by Fujie et al. (2020). The thick-sediment area is based on the MCS reflection profiles and drilling results (Moore et al. 2015; Shipboard Scientific Party 1980). The thin-sediment area is interpreted based on OBS RF and the existence of the nearby petit-spot clusters. The key point of the thin-sediment area model is that the bottom of the original sediment is heavily disturbed and metamorphosed by recent magmatic intrusions

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