Dynamics of outer‐rise faulting in oceanic‐continental subduction systems

Abstract

[1] During subduction, bending of downgoing oceanic lithosphere gives rise to normal faulting due to the extensional stress state generated in the upper plate. As deformation patterns inherently reflect a material's state of stress and rheology, extensive global observations of outer-rise faulting patterns and subduction dynamics provide a unique opportunity to examine the factors controlling outer-rise deformation. Despite a wide range of observed oceanic plate ages, convergence rates and slab pull magnitudes across modern subduction systems, however, measured outer-rise faulting patterns show effectively no correlation to variations in these parameters. This lack of correlation may reflect that outer-rise faulting patterns are strongly sensitive to all of these parameters, are dependent on additional parameters such as downgoingoverriding plate coupling or that existing faulting measurements require additional analysis. In order to provide a basis for future analysis of outer-rise faulting patterns, we build on previous thermo-mechanical numerical models of outer-rise deformation and explore the relationship between outer-rise faulting patterns, subduction dynamics and brittle rheology in an oceanic-continental subduction system. Analysis of timeaveraged outer-rise faulting patterns indicates that downgoing plate age and velocity, downgoing-overriding plate coupling and slab pull all significantly affect faulting patterns, while variations in brittle rheology have a significantly smaller impact. These relationships reflect that the sensitivity of outer-rise faulting patterns to the frictional properties of the oceanic crust and mantle is small compared to variations in the overall stress state and deformation rate of subduction systems. In order to gain additional insight into the origin outer-rise faulting patterns, future numerical studies should focus on specific regions in order to place constraints on the structure of the downgoing plate and dynamics of the subduction system.Components: 9,895 words, 9 figures, 2 tables.

Outer-rise normal fault development and influence on near-trench décollement propagation along the Japan Trench, off Tohoku

“…Furthermore, average fault spacing of 2 km is on the same order as predicted in some modeling studies (Faccenda et al 2009), although other models generate larger fault spacing of up to 10 km (Naliboff et al 2013), which is the maximum fault spacing we observe.…”

Four‐dimensional numerical modeling of crustal growth at active continental margins

“…Lithologically, 3 km thick basalt crust is thus resolved with 1.5 cells and six markers, which is enough to localize deformation in basaltic crust along the plate interface [ Gerya and Meilick , ; Faccenda et al ., ]. Two‐dimensional resolution tests for this type of subduction model are presented elsewhere [ Faccenda et al ., ; Naliboff et al ., ].…”

Subduction zone megathrust earthquakes

“…Fluids enter the shallow seismogenic system either within the pore space of the subducting igneous crust and sediment, or bound in hydrous minerals. Normal faulting associated with bending of the subducting plate is likely to produce enhanced hydration of the crust and upper mantle seaward of the subduction zone (e.g., Ranero et al, 2003;Naliboff et al, 2013;Korenaga, 2017;Grevemeyer et al, 2018). These fluids are released either through compaction in the shallowest 5-7 km or in dehydration reactions at higher pressures and temperatures (e.g., Saffer and Tobin, 2011).…”