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stage, when most of the uplifts with drape folding over the edges came into existence by
upthrusting of the basement domino blocks along the master faults. This created first-order
marginal flexures over the foothill uplifts. Lateral motion during the drift stage of the
plate induced horizontal stress and near-vertical normal faults, which were reactivated as
reverse faults during initiation of the inversion cycle, and became strike-slip faults involving
right-lateral slip, which shifted the uplifts progressively eastward relative to each other
from south to north. This resulted in the present
en echelon
positioning of the uplifts with
respect to the Kutch Mainland uplift. The strike-slip related structural changes modified
the linear flexures, breaking them into individual folds at the restraining and releasing
bends. Narrow deformation zones complicated by second-order folds and conjugate Riedel
Syntectonic intrusions further modified the shape and geometry of the individual second-
order structures. Igneous rocks extensively intruded the Mesozoic sediments during rifting
intrusive rocks and seismological data suggest the presence of mafic/ultramafic magmatic
Inversion continued during the post-collision compressive stress regime of the Indian
plate and the KR basin became a shear zone with transpressional strike-slip movements
tectonic phase is continuing, as evident from neotectonic movements along these faults
that are responsible for the present first-order geomorphic features and seismicity. In the
current tectonic cycle, under N-S compressive stresses, the NWF and SWF are the most
active faults, as evident from the concentration of aftershock hypocenters in the overlap
responsible for generation of new fault fractures within the respective deformation zones.
These new fractures are propagating through the recent piedmont and scarp-fan sediments
in the frontal zones of the thrusts, as seen in the trenches dug close to the KMF and KHF
features also indicate Quaternary uplift along the above-mentioned master faults (Malik
During the present compressive stage, the Radhanpur Arch acts as a stress barrier for
eastward movements along the principal deformation zones, which is creating additional
the eastern end of the Mainland uplift, the right lateral KMF becomes the SWF by left-
This overstep zone - formed initially as the Samakhiali-Lakadiya graben - is presently
a convergent transfer zone undergoing transpressional stress in the strained eastern part
of the basin. This is the most strained part of the basin. Expectedly, this is the most
favored site for rupture nucleation. The occurrence of the 2001 Bhuj quake (M
w
7.7) in