Active deformation and relief evolution in the western Lurestan region
of the Zagros mountain belt: new insights from tectonic geomorphology
analysis and finite element modeling
Abstract
2-D finite element modeling of both coseismic and interseismic
deformation was performed along a transect across the seismogenic fault
of the Mw=7.3, November 2017 Lurestan earthquake (Zagros Mountains). In
order to extract information on the time-space distribution of uplift
along the same transect, an investigation of the large-scale features of
topography and river network was also carried out. Constraints from the
spatial distribution of mean elevation, local relief and normalized
channel steepness index (ksn), combined with those from river
longitudinal profiles and transformed river profiles (chi-plots), were
integrated with the results of geomorphological analyses aimed at the
reconstruction of the development of the fluvial network. Despite the
much longer timescale over which topography grows and/or rivers respond
to tectonic or climatic perturbations with respect to even multiple
seismic cycles, the outputs of the finite element model yield
fundamental information on the source of the late part of the
spatiotemporal evolution of surface uplift recorded by the
geomorphological signature. Model outputs shed new light into the
processes controlling relief evolution in an actively growing mountain
belt underlain by a major blind thrust. They point out how co-seismic
slip controls localized uplift of a prominent topographic feature –
defining the Mountain Front Flexure – located above the main upper
crustal ramp of the principal basement thrust fault of the region, while
continuous displacement along the deeper, aseismic portion of the same
basement fault controls generalized uplift of the whole crustal block
located further to the NE, in the interior of the orogen.