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Allah Kausar, Geological Survey of Pakistan (Pakistan)
Heitaro Kaneda, Geological Survey of Japan (Japan)
Takashi Nakata, Hiroshima Institute of Technology, Japan (Japan)
Hisao Kondo, Geological Survey of Japan (Japan)
Sardar Akhtar, Geological Survey of Pakistan (Pakistan)
David Petley, Durham University (United Kingdom)
Mohammad Latif, Geological Survey of Pakistan (Pakistan)
Simon Sadiq, Geological Survey of Pakistan (Pakistan)
Abdul Majid, Geological Survey of Pakistan (Pakistan)
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The 8th October 2005 Kashmir earthquake of Mw 7.6 struck the northwestern margin of the Indian-Eurasian collision zone. Although no surface ruptures have been found along the Himalaya since 1800, the 2005 event was accompanied by a distinctive and extensive thrusting surface rupture. The Balakot-Bagh earthquake rupture is complex, as befits most thrust earthquakes ruptures, with considerable shallow deformation in the hanging wall, but it is clear in most places. Most of the surface rupture faithfully follows the trace of a geomorphologically-evident active Balakot-Bagh fault. The surface rupture trace on which earthquake occurs is generally not continuous, and is commonly composed of three geometrical segments separated by small steps. The mean vertical slip rate, horizontal shortening rate, and net slip rate of this fault are calculated to be 1.1-1.7, 1.9-2.9, and 2.3-3.3 mm/yr, respectively. The horizontal shortening rate across the Balakot-Bagh fault is only 10-20 % of the shortening across the Himalaya of 11.9 mm/yr and 21 mm/yr suggesting that the fault is not the major agent of the Himalayan contraction accommodation, but a relatively minor active fault formed on the overridden side, most likely rooted in the Main Himalayan Thrust (MHT). The result of trench at Nisar Camp, near Muzaffarabad, AJ&K across the restraining step between the northern and central segments yields estimates of ca. 2000-2500 years, which is much larger than that expected for the tectonic setting of the collision zone. Given our observations showing evidence that 2005 Kashmir earthquake event did not occur on the MHT, but on intra-plate active faults inside the Sub-Himalaya.
The Kashmir earthquake involved slope failures in both bedrock and superficial deposits, with landslides occurring on many natural slopes and artificially cut slopes, and were responsible for an estimated 25,000 deaths.The distribution of landslides appears to be very asymmetric and the most obvious landslides occur on the hanging wall of the fault associated with white dolomitic limestone in the area north and north-west of Muzaffarabad towards Balakot.
While not every landslide results in catastrophe, the damage from many small ones may equal or exceed the impact of a single major failure. Thus, both large and small landslides are capable of causing significant damage and loss of life. Determining the extent of landslide hazard requires identifying those areas which could be affected by a damaging landslide and assessing the probability of the landslide occurring within some time period. However, the presence of the cracked slopes also raises some fundamental questions about one of the key techniques for assessing the hazards associated with earthquake-triggered landslides. As a result, there is a high level of threat to the population of Kashmir and NWFP, and the landslides represent a significant potential source of problems during the rehabilitation phase in the country.
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