The continental collision process has made a large contribution to continental growth
and reconfiguration of cratons throughout Earth history. Many of the mountain belts
present today are the product of continental collision such as the Appalachians, the
Alps, the Cordillera, the Himalaya, the Zagros, and the Papuan Fold and Thrust Belt.
Though collisional mountain belts are generally elongate and laterally continuous,
close inspection reveals disruptions and variations in thrust geometry and kinematics
along the strike of the range. These lateral variations typically coincide with cross
structures and have been documented in thrust fault systems with a variety of geometries
and kinematic interpretations. In the Himalaya, cross faults provide segment boundaries
that, in some cases separate zones of differing thrust geometry and may even localize
microseismicity or limit areas of active seismicity on adjacent thrust systems. By
compiling data on structural segmentation along the length of the Himalayan range,
we find lateral variations at all levels within the Himalaya. Along the Gish fault
of the eastern Indian Himalaya, there is evidence in the foreland for changes in thrust-belt
geometry across the fault. The Gish, the Ganga, and the Yamuna faults all mark boundaries
of salients and recesses at the mountain front. The Benkar fault in the Greater Himalayan
sequence of eastern Nepal exhibits a brittle-ductile style of deformation with fabric
that crosscuts the older thrust-sense foliation. Microseismicity data from several
regions in Nepal shows linear, northeast-striking clusters of epicenters sub-parallel
to cross faults. The map pattern of aftershock data from the 2015 Nepal earthquakes
has an abrupt northeast-trending termination on its eastern side suggesting the presence
of a structure of that orientation that limited slip. The orientations of the recognized
cross faults and seismic patterns also align with the extensional zones to the north
on the Tibetan Plateau and the Indian basement structures to the south. Results from
multiple studies are consistent with a link between cross faults and either of these
structural trends to the north or south and suggest that cross faults may play a role
in segmenting deformation style and seismic activity along the length of the Himalaya.
