Proceedings of the Second World Landslide Forum – 3-7 October 2011, Rome Rustam Niyazov (1) , Bakhtiar Nurtaev (2) Modern seismogenic landslides caused by the Pamir - Hindu Kush earthquakes and their consequences in Central Asia (1) Institute Hydroingeo, Engineering Geology, Tashkent 100041, Olimlar 64, Uzbekistan, (2) Institute of Geology and Geophysics, Department of Geophysics, Tashkent 100041, Olimlar 49, Uzbekistan, +99871 2626882, nurtaevb@gmail.com Abstract In studying the effect of seismic events to the time, place and mechanism of development of landslides and mud flows in Central Asia, special attention attracts deep earthquakes from Pamir-Hindu Kush zone. A preliminary comparative analysis of the synchronicity in time of Pamir - Hindu Kush earthquakes and the dates of formation of large landslides in the period from 1969 to 2011 showed that more than 100 cases of landslides formed in the south of Kyrgyzstan, Uzbekistan and Tajikistan.These earthquakes in the Central Asia territory induced low-frequency (1-5 Hz) prolonged (2-3 min) ground motions and in the spring time on the moist slopes causes processes of compaction, liquefaction and displacement of loess soils. Complex relationship of two spatial factors - precipitation and earthquake to origin time, place and mechanism of landslides, occurred in last years in Central Asia, are presented in examples. Keywords: large- scale landslides, earthquakes, triggering mechanism, case study Introduction The focus of landslide research has historically been on where they have occurred, but today, more emphasis is placed on the timing of landslides. Many authors place the triggering factor as short, intense rainfall (Wieczorek and Glade, 2005) often associated with a certain quantity of rainfalls before the event. Most authors agree that these techniques are valid in a specific geological - geomorphological - climate context and cannot be applied directly to other situations. Features of combination of two external spatial factors (atmospheric) rainfall and earthquakes on the time and place of formation of the local slope of the landslide have a very complex relationship. It is due to that seasonal conditions of moist slopes can increase its susceptibility to seismic vibrations for the orders (Keefer, 1984). This paper examines modern seismogenic landslides in loess and sandy-clayey rocks, of different types such as extrusion, block, liquefaction, debris flows formed at a considerable distance (250-600 km) from the hypocenter of the deep (180 - 220 km) Pamir-Hindu Kush earthquakes (Afghanistan). These earthquakes in the Central Asia territory induced low-frequency (1-5 Hz) prolonged (2-3 min) ground motions and in the spring time on the moist slopes causes processes of compaction, liquefaction and displacement of loess soils. The stability of the deforming rock mass reaches a threshold, after which a seemingly trivial event triggers catastrophic failure. For a better understanding of these large-scale landslides, some typical ones that occurred recently in Central Asia but were rarely reported are introduced, and their formation processes are briefly analyzed in this paper. Pamir-Hindu Kush zone of deep earthquakes For the Central Asian region the largest center of seismic activity is the zone of Pamir-Hindu Kush deep- earthquakes. Every year in this area occur about 200 earthquakes at depths of 180-250 km and 35-40% of it occurs in the spring (Lukk and Nersesov 1970). Some events are reaching M-7 and in the Central Asia territory, they produce ground motions such as 3-4 MSK units of intensity. Comparative analysis of time synchrony of Pamir- Hindu Kush earthquakes and formation of large landslides in the period from 1969 to 2011 showed that more than 200 cases of landslides formed in South Kyrghystan, Uzbekistan and Tajikistan. For example, three groups of landslides were considered. The first - massive landslides in wet years with frequent earthquakes. The second - mass manifestation of landslides in wet years, but with the lack of strong earthquakes. The third one - activation of man- made major landslides at earthquakes vibrations. Landslides in wet years with frequent earthquakes In the first group were considered 20 cases of landslides were formed in 1969, when registered greatest amount of precipitation (1640 mm/year) and in the Hindu Kush from March 5 to June 10 occurred 14 earthquakes of magnitudes from 4.5 to 5.9. This year most widely were formed mudslides in loess. They were widely distributed and were extremely dangerous due to suddenness, motions which in few minutes have had