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Summary This study concentrates on the detailed determination of the state of stress in the Wadati–Benioff zone in the lithosphere subducting under Sumatra and Java. The orientations of P‐ and T‐axes of earthquake focal mechanisms (HCMT) are used to define a system of domains in which a uniform state of stress is assumed. The method of Gephart & Forsyth is then used to determine the state of stress in each domain. We succeeded in delimiting eight domains: three (SI–SIII) in the Sumatra region and five (JI–JV) in the Java region. Domains with similar states of stress occur in both regions in similar positions. The maximum compression σ1 is perpendicular to the trench in domains SI, SII and JII, that is, within the depth range 0–165 km. The orientation of σ1 is almost parallel to the trench in domains SIII and JIII (depth range 25–225 km). The boundary between domains SII and SIII, and JII and JIII is not distinct (covering the depth range 40–165 km). It seems that the focal mechanisms belonging to domains SII and SIII, and similarly to domains JII and JIII, occur in different stress layers and that we observe an overlap of earthquakes with different focal mechanisms from two different stress‐state layers, parallel to the Wadati–Benioff zone. In domains JIV and JV, the states of stress correspond to the stress pattern observed in other subduction zones: slab‐dip‐parallel extension is observed in domain JIV (depth range 225–315 km) and slab‐dip‐parallel compression is observed in domain JV (deeper than 400 km).

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We have carried out a regional correlation analysis between the seismic structure of the lower mantle and the reconstructions of subduction sites in the past 180 Myr with the aim of estimating individual styles of slab motion over different parts of the earth. The correlation patterns obtained for three subduction branches (West Pacific, East Pacific and Alpine-Himalayan) are remarkably different. In the West Pacific, the subducting slabs tend to be stagnant beneath the 660-km discontinuity, while basically no subducted lithosphere has been detected below the depth of 1000 km. In contrast, the lithosphere subducted beneath the Americas seems to penetrate through the lower mantle continuously, showing correlation peaks at depth intervals of 800 -1100 km and 1900 -2500 km. In the AlpineHimalayan region, significant correlation has been found below the 660-km discontinuity for recent subduction and in the mid-mantle for subduction younger than 120 Myr. An increase in the correlation close to the core-mantle boundary nevertheless indicates that, under certain circumstances, the slabs can reach the bottom of the mantle in the West Pacific and in the Alpine-Himalayan regions as well. The correlation peak at a depth of around 1000 km is common to all the subduction branches. However, its depth rather varies for different subduction zones and, thus, it is not clear whether this correlation maximum may be associated with a global mid-mantle discontinuity.

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