Tectonic map of western Himalayas, Hindukush, Pamir, Karakoram and western Tibet (After Pegler and Das, 1998). Other abbreviations: MCT, Main Central Thrust; MBT, Main Boundary Thrust; ZSZ, Zanskar Shear Zone; ISZ, Indus Suture Zone; MFT, Murree Frontal Thrust; MMT, Main Mantle Thrust; MKT, Main Karakoram Thrust; NP, Naga Parbat; K and MA are the Kongur and Muztagh Ata gneiss dome between dextral Karakoram Fault and sinistral Altyn Tagh Fault. 

Contexts in source publication

Context 1

... name Hindukush derives from the Arabic for Mountains of India. The study zone (328N to 408N and 688E to 788E) includes the Hindukush, Pamir and Karakorum regions, which lie to the north of the northern apex of the Indian subcontinent. The tectonics of the region is associated with complex fault systems and with rocks of a range of geological ages. The junctions of the Himalayas, Karakorum, Pamirs, Hindukush and Kun-lun lie in this region (Fig. 1). These mountains, consisting of granites and schists, were uplifted during the Neogene period. The system is characterised by the overthrust of Cretaceous limestones onto Cenozoic shales and clays. The geology and tectonics of the Hindukush complex zone and its surrounding area have been discussed by Nikolaev et al. (1981); Desio (1975); Gansser (1977); Peive et al. (1964); Stocklin (1977). The geological structure of the area includes regional folding, striking mainly north-east and south-west, and thrusting in the Cenozoic, Mesozoic (mainly the Jurassic and Cretaceous) and Palaeozoic. The Tien-shan region is an old platform that has been subjected to tectonic movement causing subsidence, uplift and fracturing. The Afghan-Tadjik depression contains Mio- cene sediments, suggesting that prior to the initiation of the central Asian orogeny in the mid-Miocene, a small oceanic plate, now subducted, was attached to the Eurasian land mass ( Lukk et al., 1995). The northern zone is mainly Tertiary sediments, whereas the southern branch is composed of metamorphic rocks, marbles and intrusions of granodiorite (Gansser, 1964). The major faults of the Pamir and Hindukush regions are arcuate E -W trending thrusts within the Pamirs. The mountain ranges of the region are separated by major faults parallel to their trend; some of which are transcurrent in nature. A few of these faults, the Herat Fault (north of Kabul), the Chaman Fault and the mountain ranges in the Pamir Knot are reported to be seismically active, and are believed to extend down to the Moho. The Hindukush region shows recent minor faults striking NE -SW, convex towards the NW (Gansser, 1964;Chatelain et al., 1980). The Tibetan Plateau, the highest in the world with an average elevation of 5 km, lies in a complex geological and tectonic setting. Zhao and Morgan (1987) reported that before the Late Pliocene the plateau had only 1 km elevation. The Tibetan crust is almost double (70 km) the average crustal thickness of 35 km (Jin et al., 1996). The tectonic characteristics of the Tibetan Plateau have been discussed by Armijo et al. (1989); Kidd and Molnar (1988); Tapponnier (1975, 1978); Molnar and Chen (1983); Molnar et al. (1987). Verma and Reddy (1988) summarized the nature of faulting from focal mechanism solutions and reported that the plateau is characterized by predominantly normal and strike slip displacements. More- over, Shanker et al. (2002) proposed that a weak Main Himalayan Thrust below Tibet, along with initiation of the Main Central Thrust, could explain the coeval development of the South Tibetan Detachment. These studies showed that active tectonics is dominated by E -W extension. Strike - slip mechanisms show left-lateral displacement along easterly extending faults, and right-lateral displacement along northerly to northwesterly striking faults Molnar, 1977, ...

Context 2

... seismicity and stress of the northern boundary of Indian Plate have been studied by Nowroozi (1971Nowroozi ( , 1972; Verma et al. (1980); Billington et al. (1977); Singh and Shanker (1993); Shanker and Singh (1995). The distribution of events and stress in the Hindukush -Pamir and the Burmese Arc are quite different. In order to understand the seismicity of the Hindukush zone it is necessary to look at the Pamir -Hindukush-Karakorum region as a whole as the seismicity has a different character at different places. During this study the seismicity of the Hindukush region and adjoining areas (308 to 408N and 658 to 808E) has been re-examined using 15 years of seismic data ( Fig The Hindukush and Pamir zones show very high seismic activity in comparison to the surrounding areas. Intermedi- ate earthquakes are confined to two seismic zones OP and PQ ( Fig. 2A and B). One zone (OP) strikes east -west at 36.58N, extending from 69.58E, and the other (PQ) NE -SW from 70.58E to 738E. The total length of both seismic zones is about 500 km, with an average width of 75 km at the surface. At the surface the zone of seismic activity is at its maximum width around (36.58N, 70.58E), decreasing on either side. Similar observations were reported by Billington et al. (1977) and Nowroozi (1972). Another remarkable feature is the clustering of events in the depth range 70 -200 km in a small area around (38.258N, 73.758E). For the east -west striking segments, the majority of the events are observed around 200 km depth, from 69.58E to 718E at 36.58N, whereas, along the northeast zone, the frequency and depth increase linearly from (37.58N, 738E) towards the southwest. A third group of events to the northwest of the Hindukush region forms an arcuate pattern, convex towards the northwest. These events extend over a zone parallel to the strike of the northwestern boundary of Tibetan Plateau ( Figs. 1 and 2). The distribution of seismicity is clearer in Fig. 3b showing the depth distribution, showing the absence of seismicity at some ...

Context 3

... are several zones of intermediate and deep focus earthquakes that are not well defined as subduction zones. These zones are Hindukush -Pamir, Burmese Arc, and the seismic nest of Bucaramanga, in Columbia ( Schneider et al., 1987;Malave and Suarez, 1995). Of these seismic zones, the Hindukush and Burmese arcs are situated on the northwest and northeast flanks of the northern boundary of the Indian Plate where intermediate focal depth earthquakes lie within the dipping seismic slab and do not well define subduction zones (Fig. 1). In the Hindukush and Burmese arcs the dip of the subduction zones defined by the earthquake foci are almost vertical. Steep dipping subduc- tion does not occur in nature, and hence these steep zones may be the result of the convergence of the surrounding plates. Some unique features of the zone of steeply dipping lithosphere, in the seismic belts of the Hindukush and the Burmese arcs is the size, the occurrence of an anomalous region of intermediate earthquakes, sharp changes in the direction of compressive stress and the orientation of tensile stresses in NE -SW and N -S ...