Relationship between outer forearc subsidence and plate boundary kinematics along the Northeast Japan convergent margin

Abstract

[1] Tectonic erosion along convergent plate boundaries, whereby removal of upper plate material along the subduction zone interface drives kilometer-scale outer forearc subsidence, has been purported to explain the evolution of nearly half the world's subduction margins, including part of the history of northeast Japan. Here, we evaluate the role of plate boundary dynamics in driving forearc subsidence in northeastern Japan. A synthesis of newly updated analyses of outer forearc subsidence, the timing and kinematics of upper plate deformation, and the history of plate convergence along the Japan trench demonstrate that the onset of rapid fore-arc tectonic subsidence is contemporaneous with upper plate extension during the opening of the Sea of Japan and with an acceleration in convergence rate at the trench. In Plio-Quaternary time, relative uplift of the outer forearc is contemporaneous with contraction across the arc and a decrease in plate convergence rate. The coincidence of these changes across the forearc, arc, backarc system appears to require an explanation at the scale of the entire plate boundary. Similar observations along other western Pacific margins suggest that correlations between forearc subsidence and major changes in plate kinematics are the rule, rather than the exception. We suggest that a significant component of forearc subsidence at the northeast Japan margin is not the consequence of basal tectonic erosion, but instead reflects dynamic changes in plate boundary geometry driven by temporal variations in plate kinematics. If correct, this model requires a reconsideration of the mass balance and crustal recycling of continental crust at nonaccretionary margins.

Slip Inversion Along Inner Fore‐Arc Faults, Eastern Tohoku, Japan

“…(c) Map showing the distribution of faults with known extension, contraction, and inversion histories, and the locations of sediment cores used to determine back‐arc and fore‐arc subsidence histories. Timing and kinematics in Figures 12b and 12c after Tamaki and Kobayashi (), Jolivet and Tamaki (), Ingle (), Okamura et al (), Takano (), Sato et al (), Okamura (), Sato et al (), Nakajima (), Okada and Ikeda (), and Regalla, Kirby, et al ().…”

“…Miocene extensional faulting in the inner fore arc along the Oritsume and Futaba Faults during the opening of the Sea of Japan was associated with crustal thinning, rift‐related tectonic subsidence, and approximately trench orthogonal σ h ‐min directions (Ingle, ; Sato, ). Extension related to the opening of the Sea of Japan was also associated with widespread tectonic subsidence in the back arc between ~25 Ma and ~15 Ma (Ingle, ) and in the outer fore arc from ~25 to 5 Ma (Arthur et al, ; von Huene et al, 1982; Regalla, Fisher, et al, ) (Figure ). This period of tectonic subsidence was coeval with the rapid deepening of the sediment‐water interface recorded in the hanging wall of the Oritsume and Futaba Faults from ~26 to 16 Ma (Figures , and ).…”

“…This transition initiated contraction across a network of faults in the upper plate, many of which evolved as inverted extensional structures (Okada & Ikeda, ; Okamura, ; Okamura et al, ; Sato & Amano, ). At the same time, the arc experienced a regional transition to tectonic uplift, documented in both fore‐arc and back‐arc subsidence records (Ingle, ; Regalla, Fisher, et al, ), shallowing of sedimentary facies in near coastal basins (Ingle, ; Kato et al, ; Sato, ; Sato, ) and flights of uplifted marine terraces that span >500 km of the Tohoku coastline (Koike & Machida, ; Suzuki, ). This period of regional uplift and shallowing of sedimentary facies coincides with the ~6 to 4 Ma onset of contractional faulting along the Oritsume, Noheji, and Futaba Faults in the inner fore arc.…”

“…The fore‐arc regions of subduction zones, like that of Northeast Honshu, Japan, are constructed and deformed over multiphase histories and evolve in response to changes in the subducting bathymetry (e.g., Audin et al, ; Bangs et al, ; Fisher et al, ; Gardner et al, ; Hampel, ; Kington & Tobin, ; Morell et al, ; Regard et al, ; Wang & Bilek, ), convergence rate and obliquity (e.g., Allmendinger & González, ; Morell, ; Regalla, Fisher, et al, ), mechanical properties of the megathrust (e.g., Allmendinger & González, ; Buiterr et al, ; Hassani et al, ; Saffer & Tobin, ), and variations in slab geometry (e.g., Capitanio et al, ; Capitanio et al, ; Royden & Husson, ). Variations in stress state during such deformation events can lead to the development of networks of upper plate faults that can act as structural weaknesses available to be reactivated in response to subsequent changes in boundary conditions at the plate interface.…”

“…The Tohoku margin of northern Japan is an example of a subduction fore arc that contains a network of inherited faults that have accommodated permanent strain in response to changes in stress state over the Jurassic to present (Ikeda et al, ; Jolivet, Tamaki, & Fournier, ; Okada & Ikeda, ; Regalla, Fisher, et al, ; Sato & Amano, ) (Figure ). Today, active E‐W directed upper plate contraction occurs over a >500 km wide region inboard of the Japan trench, across both the fore arc and the back arc (e.g., Ikeda et al, ; Okamura, ; Regalla et al, ; Sato et al, ; Wesnousky et al, ).…”