Tectonophysics 483 (2010) 327–343 Contents lists available at ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto Active fault, fault growth and segment linkage along the Janauri anticline (frontal foreland fold), NW Himalaya, India Javed N. Malik a,⁎, Afroz A. Shah a,1, Ajit K. Sahoo a,2, B. Puhan a, Chiranjib Banerjee a, Dattatraya P. Shinde b, Navin Juyal b, Ashok K. Singhvi b, Shishir K. Rath a a Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, UP, India b Physical Research Laboratory, Ahmedabad 380 009, Gujarat, India article info abstract Article history: The 100 km long frontal foreland fold — the Janauri anticline in NW Himalayan foothills represents a single Received 27 October 2009 segment formed due to inter-linking of the southern (JS1) and the northern (JS2) Janauri segments. This Accepted 30 October 2009 anticline is a product of the fault related fold growth that facilitated lateral propagation by acquiring more Available online 10 November 2009 length and linkage of smaller segments giving rise to a single large segment. The linked portion marked by flat-uplifted surface in the central portion represents the paleo-water gap of the Sutlej River. This area is Keywords: comparatively more active in terms of tectonic activity, well justified by the occurrence of fault scarps along Active faults Fault related fold growth the forelimb and backlimb of the anticline. Occurrence of active fault scarps on either side of the anticline Lateral propagation of fault suggests that the slip accommodated in the frontal part is partitioned between the main frontal thrust i.e. the Segment linkage Himalayan Frontal Thrust (HFT) and associated back-thrust. The uplift in the piedmont zone along southern Paleoseismology portion of Janauri anticline marked by dissected younger hill range suggests fore-landward propagation of NW Himalaya tectonic activity along newly developed Frontal Piedmont Thrust (FPT), an imbricated emergent thrust branching out from the HFT system. We suggests that this happened because the southern segment JS1 does not linked-up with the northwestern end of Chandigarh anticline segment (CS). In the northwestern end of the Janauri anticline, due to no structural asperity the tectonic activity on HFT was taken-up by two (HF1 — in the frontal part and HF2 — towards the hinterland side) newly developed parallel active faults (Hajipur Fault) branched from the main JS2 segment. The lateral propagation and movements along HF1 and HF2 resulted in uplift of the floodplain as well as responsible for the northward shift of the Beas River. GPR and trench investigations suggest that earthquakes during the recent past were accompanied with surface rupture. OSL (optical stimulated luminescence) dates from the trench suggests occurrence of at least two events during the recent historic past, with the latest — Event II during 1500 AD (?). © 2009 Elsevier B.V. All rights reserved. 1. Introduction represent the principal intracrustal thrusts: the Main Central Thrust (MCT), Main Boundary Thrust (MBT), and Himalayan The tectonic collision between Indian and Eurasian plates has Frontal Thrust (HFT), with younger initiation ages towards the made the Himalayan arc as one of the most seismically active south (Thakur, et al., 2007). The strain accumulated across the regions of the world. Since collision (∼50 Ma) along the Indus– Himalayan zone due to ongoing deformation has been episodically Tsangpo Suture Zone, the successive zones of deformation have released in form of large to moderate magnitude earthquakes in progressively advanced southward, resulting in faulting and folding the region. The recent 2005 (Mw 7.6) Muzaffarabad earthquake has along the prominent structural features of the Himalayan orogenic again proved the capability of the Himalaya in producing large belt (Gansser, 1964; Seeber et al., 1981; Lyon-Caen and Molnar, magnitude earthquakes. Field investigations revealed a rupture of 1983). From north to south these prominent structural features about 65 km along an earlier identified “Tanda active fault” having lateral extend of about 16 km (Nakata et al., 1991; Kaneda et al., 2006; Yeats and Hussain, 2006). These earthquakes have raised ⁎ Corresponding author. concerns toward the seismic hazard assessment in Himalaya, E-mail addresses: [email protected] (J.N. Malik), [email protected] (A.A. Shah), especially in the foothill zones bordering the thickly populated [email protected] (A.K. Sahoo), [email protected] (D.P. Shinde), Indo-Gangetic Plain. Apart from few large magnitude events in NW [email protected] (N. Juyal), [email protected] (A.K. Singhvi). Himalaya with M≥ 7.6 viz. 1555 and 1885 Kashmir events; 1905 1 Now at School of Earth & Environmental Sciences, James Cook University, Townsville Queensland 4811, Australia. Kangra and recent 2005 Muzaffarabad, no historical records are 2 Now at Reliance India Limited, Mumbai. available from this region. In seismically active regions of the 0040-1951/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2009.10.028 328 J.N. Malik et al. / Tectonophysics 483 (2010) 327–343 Fig. 1. (a) DEM of the area around NW Himalaya showing prominent NNW–SSE striking frontal foreland fold — the Janauri anticline. Inset shows map of India with location of Janauri anticline and study area, (b) Profile AA` is across the Hajipur fault in the northwestern fringe of Janauri anticline, (c) BB` is drawn in the central part of Janauri anticline, and (d) CC` is across the southern fringe showing the Frontal Piedmont Thrust. HFT — Himalayan Frontal Thrust, BT — Back Thrust, SnT — Soan Thrust and NaT — Nalagarh Thrust. J.N. Malik et al. / Tectonophysics 483 (2010) 327–343 329 world, active faults are considered to be the source for large 2. Geomorphology magnitude earthquakes, and the paleoseismic investigations along such faults have proved their capability in producing large earth- 2.1. Geomorphological setting and active fault distribution quakes periodically (e.g. Nakata, 1989; McCalpin, 1996; Yeats et al., 1997; Meghraoui and Doumaz, 1996; Oatney et al., 2001; The area along the NW Himalayan foothill zone shows three major Meghraoui et al., 2003; Malik and Nakata, 2003; Pantosti et al., geomorphic zones (Figs. 1 and 2) from north to south. These zones are 2004; Malik and Mathew, 2005; Lavé et al., 2005; Kumar et al., bounded by major fault lines (Fig. 1a). The longitudinal intermontane 2006; Kaneda et al., 2006; Yeats and Hussain, 2006). It is therefore valley — Soan Dun (Dun= valley) is the northern most major extremely important to have precise active fault map in the region geomorphic unit in the study area. The Soan Dun is confined between like Himalaya, where not much information is available on the the Lower Siwalik Hills to its north and the Sub-Himalayan range (Upper distribution of active faults. Because without such studies the Siwalik) in south. The boundary between the Lower Siwalik Hills and hazard posed by these faults may be underestimated. Soan Dun is marked by Nalagarh Thrust (NaT) and the southern limit by The studies on active tectonic deformation in the Himalayan frontal Back-thrust (BT) along the back-limb of Janauri anticline. The Sub- zone from Nepal and India have revealed occurrence of uplifted-tilted Himalayan range marked by the Janauri anticline represents the late Pleistocene and Holocene fluvial terraces and alluvial fan surfaces, youngest foreland fold demarcating the southern boundary the with prominent fault scarps ranging in height from 5 to 50 m resulted Himalaya with respect to the Indo-Gangetic Plain (IGP) to its south. due ongoing active deformation along the Himalayan Frontal Thrust This vast flat alluvial plain (IGP) represents the present foreland basins (HFT), Main Dun Thrust (MDT) and the Main Boundary Thrust (Nakata, 1972; Powers et al., 1998; Malik and Mohanty, 2007). (MBT) (Nakata, 1972, 1975; Valdiya, et al., 1984; Nakata, 1989; Nakata The boundary between the Janauri anticline and Indo-Gangetic Plain is et al., 1990; Valdiya, 1992; Yeats et al., 1992; Mugnier et al., 1998; marked by Himalayan Frontal Thrust (HFT). Wesnousky et al., 1999; Lavé and Avouac, 2000; Malik and Nakata, The Sutlej and Beas Rivers emerging from higher Himalayas are the 2003; Malik et al., 2003; Mugnier et al., 2004). However, still there are major drainage in the region (Figs. 1–3). The Beas River borders to the several areas particularly in NW Himalaya were very little information northern fringe of the Janauri anticline and Sutlej River to its south is available. before debauching on the Indo-Gangetic Plain. The growth of the Along with active fault identification it is important to know the 100 km long Janauri anticline has influenced the flow paths of these pattern of deformation, which in turn, helps in understanding the major rivers. The flat topped uplifted surface in the central part of the overall evolution of the landscape and also towards identifying the anticline marks the paleo-water gap of Sutlej River and a linked-up geometry of the fault related fold segments. Frontal fault-propaga- segment formed by the linkage of two smaller fault segments (Malik tion fold growth in forward as well as lateral directions are and Mohanty, 2007). commonly noticed in active fold-and-thrust belt (e.g. Mueller and Talling, 1997; Delcaillau et al., 1998; Champel et al., 2002; Delcaillau 3. Active fault distribution along Janauri anticline et al., 2006; Malik and Mohanty, 2007; Simoes et al., 2007). Lateral propagation of fault and related development of fold to some extent Several traces of active fault scarps were identified in the central has been attributed to slip along the fault during major earthquakes portion along the Janauri anticline by Malik and Mohanty (2007),butno (Walsh et al., 2002). It has been suggested that fault and associated ground truthing was carried out.