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Migration Imaging of the Java Subduction Zones
Author(s) -
Dokht Ramin M. H.,
Gu Yu Jeffrey,
Sacchi Mauricio D.
Publication year - 2018
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2017jb014524
Subject(s) - geology , slab , subduction , classification of discontinuities , seismology , discontinuity (linguistics) , trench , transition zone , mantle (geology) , underplating , petrology , geophysics , tectonics , mathematical analysis , chemistry , mathematics , organic chemistry , layer (electronics)
Imaging of tectonically complex regions can greatly benefit from dense network data and resolution enhancement techniques. Conventional methods in the analysis of SS precursors stack the waveforms to obtain an average discontinuity depth, but smearing due to large Fresnel zones can degrade the fine‐scale topography on the discontinuity. To provide a partial solution, we introduce a depth migration algorithm based on the common scattering point method while considering nonspecular diffractions from mantle transition zone discontinuities. Our analysis indicates that, beneath the Sunda arc, the depth of the 410 km discontinuity (the 410) is elevated by 30 km and the 660 km discontinuity (the 660) is depressed by 20–40 km; the region of the strongest anticorrelation is correlated with the morphology of the subducting Indo‐Australian slab. In eastern Java, a “flat” 410 coincides with a documented slab gap, showing length scales greater than 400 km laterally and 200 km vertically. This observation could be explained by the arrival of a buoyant oceanic plateau at the Java trench at approximately 8 Ma ago, which may have caused a temporary cessation of subduction and formed a tear in the subducting slab. Our results highlight contrasting depths of the 410 and 660 along the shallow‐dipping slab below the Banda trench. The 660, however, becomes significantly uplifted beneath the Banda Sea, which is accompanied by enhanced reflection amplitudes. We interpret these observations as evidence for a subslab low‐velocity zone, possibly related to the lower mantle upwelling beneath the subducting slab.