Active Tectonic Strike-Slip Fault Development near Goran, Samba and Kathua Districts, Jammu and Kashmir

Active tectonic morphometric studies of the sparsely investigated frontal Siwalik terrain around Goran in the Samba district bordering the Kathua district of J&K reveal the presence of NW-SE trending active sinistral strike-slip fault with oblique slip component which is parallel to the Surin-Masatgarh anticline. The Basantar River, the Tarnah stream, the Ujh River, the Sahaar stream and the Ravi River exhibit significant stream offsets where the fault crosses these channels. The values of the morphometric indices viz. stream sinuosity index (S), stream length gradient index (SL), valley floor width to valley height ratio (V f ), mountain front sinuosity index (S mf ), hypsometric integral (Hi), basin asymmetry ratio (AF) and basin elongation ratio (Eb) calculated along the linear river offsets with respect to longitudinal River segments of the Rivers Basantar, Tarnah, Ujh, Sahaar and Ravi Rivers reveal that terrain is tectonically active and can be placed in tectonic active class I. The fault has an apparent offset of about 2000 m with it as it crosses the Basantar, the Tarnah, the Ujh, the Sahaar and the Ravi Rivers. The stream offsets upon field and laboratory investigations are developed due to an active sinistral strike slip fault which is being named as Goran fault. This fault has a surface expression of 100 km extending from the Basantar in the northwest up to the Beas River in the southwest whereas the remaining segment may exist as a hidden fault all along the Himalaya.

front of the Himalayan orogenic belt [1]. The thrust faulting in the frontal Himalayan terrain is strongly influenced by the spatial and temporal patterns of active deformation recorded on the margin of the orogenic belts. The accumulated strain on account of the continuous northward migration of the Indian plate finds frequent release in the form of seismic events that display a conspicuous inter-relationship amongst the basal decollement surface, rate of thrusting and plate motion rates [2] [3] [4]. The data emerging from the spectacular surface rupturing earthquakes suggest that the current tectonic activity is primarily occurring in the frontal thrust terrain [5]. Active tectonic morphometric studies within the orogenic belts are of significant importance in the context of evaluating the models of deformation, thrust belt kinematics, as also the seismic hazard faced by the population habiting in close proximity to the active faults. [6] discussed the neotectonic activities that have occurred in the Himalayan terrain. [7] described the structure and shortening of the Kangra and Dehra Dun re-entrants of Sub-Himalaya. [8] has done reassessment of earthquake hazard based on a fault-bend fold model of the Himalayan plate. [9] has described the palaeo-seismicity and seismic hazard assessment in the Himalaya. [10] has identified and described the uplift and convergence along the Himalayan Frontal thrust of India. [11] has identified and described neo-tectonic activity near Nada village and Morni Hills in the Himalayan foothills. [12] described the earthquake recurrence and rupture dynamics of Himalayan Frontal Thrust. [13] discussed the convergence across the northwestern Himalaya. [14] discussed reactivation of Himalayan frontal fault system and its implications. [15] described the shutter ridges and sag ponds along the Jainti Devi Fault near Chandigarh. [16] [17] described the neotectonic and seismo-tectonic characterization of the frontal Himalayan terrain. [18] documented recent fold growth and drainage development in the Janauri and Chandigarh anticlines of the Siwalik foothills. The neotectonic activity in the Markanda and Bata River Basins in Himachal Pradesh has been investigated by [19] and their study suggested upliftment and tilting of the Markanda and Bata River Basins due south. Seismites occurring in the frontal Himalayan terrain near Panchkula in Haryana were identified by [20]. [21] assessed the tectonic character of the terrain in the Frontal Siwalik hills near Trilokpur, northwestern Himalaya using remote sensing and tectonic morphometric approach. A comprehensive evaluation of the tectonic morphometric indices in terrain characterization has been attempted by [22]. Besides [23] [24] [25] [26] [27] have also worked on active tectonic aspects in the frontal Himalayan terrain of the northwestern Himalaya. The present study is aimed at identifying the active tectonic elements in the Kashmir Himalaya, especially in the region between the Basantar and the Ravi Rivers, as the Kashmir Himalaya has been considered to represent a seismic gap due to non-availability of historical earthquakes in this region [28] [29] except Kangra earthquake in 1905 and Uri-Muzzafrabad earthquake in 2005.

Geological Setup
The Middle Miocene to Middle Pleistocene (23.5 m.a. to 1.6 m.a.) Siwalik group The rocks of the Siwalik group in study area occur as an asymmetrical anticline referred to as the Surin-Masatgarh anticline. The rocks exhibit N50˚W -S50˚E trend with the dominant SW dip direction. The Surin-Masatgarh anticline marks the thrust front [34]. The folding of this anticline has been estimated on the basis of palaeomagnetic data and thermo chronometry. Detritial apatite studies by [35] suggests onset of folding before 2 m.a., while the palaeomagnetic data by [31] [36] suggests an age between 1.6 to 2.1 m.a.

Field Observations
The southern limb of the asymmetrical Surin-Masatgarh anticline between the Ravi River and the Basantar River is 60 km in length and 20 km wide at Basantar re-entrant and 10 to 12 km wide at Ravi re-entrant. The major geomorphic fea-

Methodology
The active tectonic characterization of the terrain in the vicinity of Ravi River in the frontal Siwalik terrain is carried out in a multidisciplinary manner. The data obtained from comprehensive field surveys, satellite imageries and morphometric investigations is being analyzed to ascertain the tectonics of the area of investigation. The Google Earth images ( Figure 4) and LISS-III imageries ( Figure   5) are being analyzed for visual identification and interpretation of geologic and geomorphic features.

Morphometric Analysis
Morphotectonic analysis is widely used as a basic reconnaissance tool for geomorphic evaluation of active tectonics. The morphotectonic indices computed to substantiate the role of active tectonics in research area have been briefly discussed below. The channel morphology, the fluvial processes and the hydrologi-

Stream Sinuosity Index (S)
The Stream Sinuosity index helps in understanding the affect of tectonic character of the terrain on the River course. It is defined as the ratio of the channel length (C) to the valley length (V) i.e. S = C/V by [

Stream Length Gradient Index (SL)
The Stream Length Gradient Index (SL) is the rate of change of slope and provides a quantitative measure of tectonic activity or quiescence in a basin [43].
Mathematically, it is defined as, SL = ΔH·L/ΔL, where ΔH is the change in elevation of the stream flow in the active segment and ΔL is the length of the active segment and L is the length of stream from its origin to the active segment. High SL values are indicative of high rates of tectonic uplift. SL values for the Basantar River, the Tarnah stream, the Ujh River, the Sahaar stream and the Ravi River ( Figure 6) are 345, 144, 510, 221 and 183 respectively which are high and indicate tectonically active nature of the terrain.

Valley Floor Width to Valley Height Ratio (Vf)
The  floor, E ld is the maximum elevation to the left side of the defected segment, E rd is the maximum elevation to the right side and E sc is the elevation of valley floor at the deflected segment. This is a useful index that measures effectiveness of stream down cutting in response to the tectonic uplift [44]. When calculating V f these parameters are measured at a set distance from the mountain front for every valley studied. It helps to discriminate between broad, flat floored canyons (with high values of V f as > 1) with major lateral erosion in response to base level stability or tectonic quiescence, from the V-shaped valleys (with relatively low values of V f as < 1) formed as a result of active down cutting in response to tectonic uplift. High values are reflective of low tectonic activity whereas low values are associated with tectonically active areas undergoing rapid uplift and valleys incision [45]. The V f for the Basantar River is 0.359; for the Tarnah stream is 0.750; for the Ujh River is 0.941; for the Sahaar stream is 0.739 and for the Ravi River 0.121. Low V f values varying from 0.121 to 0.941 indicate that the terrain is tectonically active.

Mountain Front Sinuosity Index (Smf)
Mountain Front Sinuosity Index is a reconnaissance tool to identify areas of tectonic activity. It is defined as the ratio of length of the mountain front (L mf ) along foot of the mountain at the pronounced break of slope to the straight line length (L s ) of the mountain front. i.e. S mf = L mf /L s . The S mf reflects the balance between erosion producing irregular/sinuous fronts and tectonic forces creating  [46]. Mountain front with lesser activity, but still reflecting active tectonics have S mf value between 1.4 and 3, whereas S mf values more than 3 reflects inactive mountain fronts [45]. The S mf value for the hill ranges along the Basantar River is 1.58; along the Tarnah stream is 1.453; along the Ujh River is 1.216; along the Sahaar stream is 1.550 and hills bordering along the Ravi River is 1.6. The S mf values along all localities are less than 1.6 that indicates the terrain is tectonically active.

Drainage Basin Asymmetry Factor (AF)
Drainage basin asymmetry analysis helps in finding out the neotectonic activity in an area. Drainage basin asymmetry has been used as a tool to identify quaternary tilting [47]. The Asymmetry Factor is a qualitative index that helps in evaluating basin asymmetry. It is defined as the AF = Ar/At, where Ar is the total area along the right side of the stream and At is the total area of the basin. In a stable environment AF is 50, whereas the value more or less suggests the tilt in the basin that represents neotectonic activity [43].

Hypsometric Integral (Hi)
The Hypsometric integral is defined as the distribution of different elevations across a landscape that can be evaluated over a small area to a large area extend-

Basin Elongation Ratio (Eb)
The Basin elongation ratio is one of the proxy indicators of neotectonic activity [44]. [49] defined the basin elongation ratio as the ratio of diameter of a circle having the same area (A) as the basin to the maximum length (L) of the basin.

Knick Points
All channels viz. the Basantar River, the Tarnah stream, the Ujh River, the Sahaar stream and the Ravi River have knick points along the River segments where the fault is crossing these channels (Figure 7). Along the knick points in the longitudinal River segment there is sudden change in the profile of the Rivers. This break in slope in a graded profile represents the trace of the active tectonic activity.

Conclusion
The terrain between the Basantar River and the Ravi River has been closely ex-