Abstract

The Sunda arc has been modelled as a test subduction zone with geometrical complexities and varying dynamics. We simulated spatially the structural heterogeneities of the subduction zone and carried out our computations by a three-dimensional finite element approach. The aim is to estimate the lateral variation in the effective horizontal compressive stress in the interplate region, which can produce the present-day observed seismogenic stress field. In our simplified approach, the stress field has been modelled by varying the traction (ridge push), while keeping the age-dependent gravitational body force (slab pull) constant. Our result suggests that there is a considerable amount of stress dissipation in the decoupled segment of Java. At Sumatra, the required traction is much greater than that expected from the age-dependency relations. In our modelling, the transition from the dominance of the horizontal compressive stress to that of the gravitational pull in the regional stress field occurs around a depth range of 150–200 km. Lateral variation in the subducted slab volume emerges crucial to the seismogenic stress field and the derived pattern of displacement. Subduction of the lighter oceanic rise material should enhance the stress level. The effect of abrupt lateral variation in structure e.g., sudden changes in the slab dip or slab depth, may also be significant on the regional stress field. Viscoelastic modelling attempted for estimating the temporal variation in subduction dynamics suggests that the thrust level will increase southward of the present day thrust zone in Java, while strike-slip fault-type stress field will be developed south of Sumatra.

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