Tectonic regime of the southern Kurile Trench as revealed by multichannel seismic lines

Abstract

The analysis of the two multichannel seismic reflection records P-855 and P-856 reveals the complexity of the tectonic structure of the Kurile margin. The absence of trench fill and the relatively constant thickness of the subducted sediments on top of the oceanic basement shows that little or no accretion is occurring at present. The lower slope is characterized by active thrusting within a small accretionary prism. The toe of the middle slope is a more consolidated unit that constitutes an efficient buttress. A piggy back basin, possibly filled by sediments that have drifted down slope, has formed on top of this unit. A narrow high marks the transition to the edge of the continental terrace. Furthermore, the upper slope reveals an unconformity marking the top of the basement. The similarity of this unconformity and its sedimentary cover with the well documented data acquired around DSDP Legs 56-57 suggests that northern Japan and the southern Kurile forearcs may have experienced a similar Cenozoic vertical history.

Physiographical and sedimentological characteristics of submarine canyons developed upon an active forearc slope: The Kushiro Submarine Canyon, northern Japan

“…2 and 5). The upper terrace is underlain by wellstratifi ed refl ectors (Schnürle et al, 1995;TuZino et al, 2006) and possibly formed via a combination of subsidence and regional tilting (Klaeschen et al, 1994). TuZino et al (2006) reported the formation of half-grabens along the upper terrace Table DR2).…”

“…The slope between the upper and lower terraces exceeds 5° and is covered by a 600-mthick series of low-amplitude refl ections oriented parallel to the slope and underlain by weakly folded Neogene sediments (Schnürle et al, 1995). Uplift of this slope might have resulted from the underplating of sediment within the subduction zone (Klaeschen et al, 1994).…”

“…14C3 and 14C4). Ridge and dome structures (Ogawa et al, 1993) developed upon the lower slope, which consists of sedimentary rocks deformed by subduction (Nakanishi et al, 2004;Schnürle et al, 1995), can be assumed to have a greater shear strength than hemipelagic sediments of the upper slope (e.g., Hempel, 1995); therefore, the substrate of the lower slope is potentially more resistant to erosion by turbidity currents than sediments of the upper slope. We consider that tectonic controls on canyon profi le might be stronger than canyon erosion along the lower segments (Fig.…”

Paleoseismicity along the southern Kuril Trench deduced from submarine-fan turbidites

“…The lower slope is bounded by the outer high that consists of non-layered acoustic basements ( Fig. 5B and C) (Honza et al, 1978;Klaeschen et al, 1994;Schnürle et al, 1995). The sediments of the lower slope represent the formation of a half-graben, suggesting Fig.…”

The South Connemara Group reinterpreted: a subduction-accretion complex in the Caledonides of Galway Bay, western Ireland

“…Even where no major de´collements are recorded, the thickness may not be original. In the Kurile trench, the pelagic sediments have been thickened tectonically by a factor of 2 as they approached the trench, and inter-tongue with distal turbidites before being subducted or accreted (Schnu¨rle et al, 1995).…”