Active Tectonics of Himalayan Frontal Fault Zone in the Sub-Himalaya

Abstract

The Himalaya grew progressively with the development of fold-thrust systems towards foreland from north to south. The Cenozoic foreland basin of the Sub-Himalaya zone was developed in front of the rising Himalaya. It is bounded between the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT). The Himalayan Frontal Fault zone encompasses the frontal anticlines, dun (intermontane basins) and hinterland fold-thrusts. The tectonic geomorphological mapping and optical simulation luminescence (OSL) dating of geomorphic surfaces/sediments indicate Late Pleistocene-Holocene deformation in the foldthrust system of the Himalayan Frontal Fault zone. The frontal anticlines are developed as fault-bend folds over the HFT. The backlimbs of the anticlines are largely characterised with formation of intermontane basins of duns. The surface ruptures of past earthquakes are recorded in paleoseismological-investigated trenches over the Himalayan front along the HFT trace, whereas epicentres of the earthquakes are in the Lesser Himalayan hinterland. The HFT represents the surface expression of the Main Himalayan Thrust (MHT). The slip generated over the earthquake rupture is transferred to the MHT-HFT. This suggests coseismic slip contributes incrementally to the growth of the frontal anticlines. Using strath surfaces over the hanging walls of reverse faults, the uplift and shortening rates are computed. The estimated shortening rates are 18-20 mm/year in the central Himalaya and 13-15 mm/year in northwest Himalaya during Late Pleistocene-Holocene. The long-term shortening rates are nearly consistent with the current rates derived through geodetic (GPS) method. In the Sub-Himalayan hinterland, there are out-of-sequence faults which show Late Pleistocene-Holocene activation. Late Pleistocene activation is observed along certain segments of the MBT. Normal faulting is ascribed largely to activation of the MBT, whereas left-lateral sense of motion along fault scarp in the alluvial fan covering the MBT is also observed.

Assessment of relative tectonic activity using morphotectonic analysis in the Central High Atlas, Demnate Region, Morocco

“…To decipher the main geomorphological features related to topography of the CHA (Demnate region), we have realized three swath profiles across the mountain belt: (Termier 1941;Bourcart and Roch 1942;Choubert et al 1970;Faure-Muret and Choubert 1975;Hindermeyer et al 1977;Jenny 1985;Alain 1985;Jossene 1990). b Lithological units and the rocks strength levels that increase from the least consolidated to the hardest in the DHA (1 to 6) based on Manrique 1988, with spatial distribution of knickpoints.…”

“…The morphotectonic and morphometric analysis using geomorphic indices is widely used and recognized in several areas on Earth, such as the Himalayas (Mahmood and Gloaguen 2012;Dar et al 2013;Lahiri and Sinha 2014), Spain (El Hamdouni et al 2008;Pedrera et al 2009;Pérez-Peña et al 2010;Giaconia et al 2012aGiaconia et al , 2012bAntón et al 2014), Italy (Troiani and Della Seta 2008;Giano et al 2018;Pavano et al 2019;Robustelli 2019), and numerous other areas including India, Iraq, Iran, Turkey, and Pakistan (Efe et al 2011;Thannoun 2013;Alizadeh et al 2020;Thakur et al 2020).…”

“…3 Geology and structural set up of the CHA. a Geologic map of the Demnate High Atlas (DHA), showing major rock units and fault systems (modified from the geologic maps of Demnate-Telouate, Ouaouizghte-Dades, Ouarzazte-Alougoum, Jebl Saghro-Dades, Azilal, Demnat, and Zawyat Ahançal)(Termier 1941;Bourcart and Roch 1942;Choubert et al 1970;Faure-Muret and Choubert 1975;Hindermeyer et al 1977;…”

An embryonic fold and thrust belt south of the Himalayan morphological front: Examples from the Central Nepal and Darjeeling piedmonts

“…In numerous cases (Fig. 1A), weak tectonic uplift has been observed in the piedmont (e.g., Thakur et al, 2020;Srivastava et al, 2017;Yeats and Thakur, 2008) south of portions of the morphologic front where the palaeo-seismological activity of the Main Frontal Thrust (MFT) has been documented (e.g., Le Roux-Mallouf et al, 2020;Wesnousky et al, 2019;Kumar et al, 2006). This uplift of the piedmont is, in some cases, linked to the lateral propagation of the frontal thrust (e.g., Almeida et al, 2018;Delcaillau et al, 2006;Champel et al, 2002), but in most cases, it is located ahead of the frontal thrust (e.g., Thakur et al, 2020;Yeats and Thakur, 2008).…”

“…1A), weak tectonic uplift has been observed in the piedmont (e.g., Thakur et al, 2020;Srivastava et al, 2017;Yeats and Thakur, 2008) south of portions of the morphologic front where the palaeo-seismological activity of the Main Frontal Thrust (MFT) has been documented (e.g., Le Roux-Mallouf et al, 2020;Wesnousky et al, 2019;Kumar et al, 2006). This uplift of the piedmont is, in some cases, linked to the lateral propagation of the frontal thrust (e.g., Almeida et al, 2018;Delcaillau et al, 2006;Champel et al, 2002), but in most cases, it is located ahead of the frontal thrust (e.g., Thakur et al, 2020;Yeats and Thakur, 2008). Present-day deformation in the proximal foreland has been suggested by spirit levelling data (Jackson and Bilham, 1994), radar interferometry (Bhattacharya et al, 2014;Yhokha et al, 2015), and GNSS data (Mullick et al, 2009); Gupta et al, 2017), but none of these studies are robust (Bilham et al, 2017).…”