Neotectonic character of Son-Narmada geo-fracture and its implication on
SCR earthquakes in central India: A geomorphic and InSAR approach.
Abstract
Apparently stable central Indian craton has been experiencing a number
of micro-seismicity in and around the pristine Son-Narmada-South fault
(SNSF), possibly because of creep along some reactivated or unidentified
fracture planes. Drainage network being highly susceptible to even
subtle active tectonics, a reconnaissance study of the area has been
carried out using river morphometric analysis. Thereafter, a Principal
Scattering Interferometry time series (PSInSAR-TS) analysis (Hooper et
al 2004, 2007) was performed to precisely locate the surface-tip of the
slip plane. And finally, the fracture geometry and orientation of the
slip vector was enumerated by integrating PSINSAR with morphometric
analysis. Generally, drainages respond to block uplift with abrupt
incision and thereby making a very narrow channel width. However,
delineating such incision from the standard Width-Depth ratio from DEM
based studies becomes difficult, because of its coarser resolution.
Therefore, considering rectangular channel flow for a stable river, the
expected width was compared with the actual width of the river measured
from high resolution Sentinel II images following the relation modified
after Finnegan et al., 2005; which states that W
=KA^(2/3)S^(-3/16), where the constant K depends on the
rectangular channel geometry, manning constant and rainfall in the area,
A is upper catchment area and S is slope of the river reaches. A NE-SW
trending zone of narrower channel width was identified with this
procedure which was interpreted as a result of block uplift, later
confirmed from the rate of uplift preliminarily calculated using an
expression derived from basic stream-power equation:
U=K(((Z(a)-Z(o))/Χ)^n) (A^m), where the uplift (U) is a function
of erodibility (K), river catchment area (A) and chi (χ) value as per
Perron and Royden 2012. PSInSAR-TS analysis of the area delineated an
average net-slip rate of 11mm/year along a number of NE-SW trending
south dipping oblique slip reverse faults, with sinistral strike slip
components, arranged in enechelon pattern and are softly linked to each
other with jogs accommodating movements in normal sense. Lastly, the
fault geometry was confirmed by comparing the deformation map generated
from the InSAR technique with the field evidence and previous studies.