To reveal the spatial distribution of major active faults and structural
discontinuities in the Himalayan-Tibetan orogen, this paper presents
wavelet multiscale analysis of the Bouguer gravity field and solves the
total horizontal derivatives of each wavelet detail. The results show
that, in general, the crustal discontinuities on the Pamir Plateau and
in the Himalayan tectonic zone are significant. On the northern margin
of Tibet, active faults are mostly visible only in the deep crust. In
eastern Tibet, crustal discontinuities decrease as depth increases. The
Himalayan crust is undergoing E-W extension, and material
discontinuities are significant along N-S-trending normal faults. The
Sangri-Nacuo fault is the tectonic boundary between the Himalayan
tectonic zone and the eastern Himalayan syntaxis and cuts off the entire
lithosphere of Tibet. The spatial structural distributions of the
western and eastern Himalayan syntaxes are very different. The former is
relatively intact and extends deeper in the lithosphere, while the
latter is more complex and shallower than the Mohorovicic discontinuity,
and its overlying crust has deformed intensely from the collision
between the Indian and Eurasian plates. Further, the structural
distribution in the upper mantle reveals that the wedging Indian plate
in the western Himalayan syntaxis almost reaches the SW margin of the
Tarim basin and forms a closed structure in western Tibet, which could
help to explain the eastward extrusion of the Tibetan Plateau.