A. Chemenda et al., Strain partitioning and interplate friction in oblique subduction zones: Constraints provided by experimental modeling, J GEO R-SOL, 105(B3), 2000, pp. 5567-5581
Physical modeling of oblique subduction is performed to study the mechanism
of strain partitioning. The model is two-layer and includes the elasto-pla
stic lithosphere (the overriding and subducting plates) and the low-viscosi
ty liquid asthenosphere. The subduction is driven by a push force from a pi
ston and a pull force when the density contrast Delta(rho) between the subd
ucting plate and the asthenosphere is positive. We vary both Delta rho and
the interplate friction (frictional stresses). Slip partitioning is obtaine
d only in the models with high interplate friction and only when the overri
ding plate contains a weak zone. This zone in the models corresponds either
to locally thinned lithosphere or to cut (fault). The horizontal, trench-n
ormal component of the interplate friction force \F-fh\ can be comparable w
ith the absolute value of the horizontal component of the nonhydrostatic in
terplate pressure force \F-Ph\ in the subduction zone. F-fh is always negat
ive (compression), while F-Ph can be either negative (compressional subduct
ion regime) or positive (extensional regime). High friction, which promotes
partitioning, can completely cancel the extensional (suction) force F-Ph B
ack are tension and strike-slip faulting appear thus as conflicting process
es, although they can coexist in the same subduction zone, depending on the
relative values of relevant forces. It appears that high friction can exis
t only in compressional subduction zones where partitioning should develop
more easily. This conclusion is supported by the comparison of two oblique
subduction zones, having similar geometry: the compressional southern Kuril
e zone (strong partitioning) and extensional southern Ryukyu zone (no litho
spheric-scale partitioning). Other factors controlling the strain partition
ing are the length of the oblique subduction zone, the boundary conditions
at the transverse limits of the forearc sliver, and of course, the obliquit
y of subduction.