Kanatbek Abdrakhmatov

Probabilistic PGA and Arias Intensity maps of Kyrgyzstan (Central Asia)

New probabilistic seismic hazard and Arias Intensity maps have beendeveloped for the territory of the Kyrgyz Republic and bordering regions.Data were mainly taken from the seismic catalogue of Kyrgyzstan and partlyfrom the world seismic catalogue. On the base of seismicity and activetectonics, seismic zones were outlined over the area. For these,Gutenberg-Richter laws were defined using mainly instrumental data, butregarding also historical events. Attenuation of acceleration inside the targetarea could not be determined experimentally since existing strong motiondata are insufficient. Therefore, empirical laws defined for other territories,principally Europe and China, were applied to the present hazardcomputations. Final maps were calculated with the SEISRISKIII programaccording to EUROCODE8 criteria, i.e. for a period of 50 years with90% probability of non-exceedance. For long-term prediction, 100 yearsmaps with 90% probability of non-exceedance have been developed. Theprocedure used for seismic hazard prediction in terms of PGA (PeakGround Acceleration) was also applied to Arias intensities in order to beable to define regional seismogenic landslide hazard maps.

Geophysical investigations of seismically induced surface effects: Case study of a landslide in the Suusamyr Valley, Kyrgyzstan

In summer 1998, a geophysical survey including seismic profilesand electrical tomography has been carried out in the Suusamyr valley, Kyrgyzstan. The scope wasto investigate surface effects induced by the Ms = 7.3 Suusamyr earthquake, the 19th of August, 1992. Inthis paper, special attention is paid to the case study of a debris slide triggered by the earthquake.Seismic data are analysed by P-wave refraction technique and by surface wave inversion. Electrical tomographicprofiles are processed by 2D-inversion.Using geotechnical and geological information, P-velocity modelsand resistivity sections are interpreted in terms of geological materials, in order to build a geological3D model. On the basis of the latter, we carried out static finite element computations as well as staticand pseudo-static calculations with Janbu’s method. Newmark displacement was computed, considering or notthe influence of the shallow soft deposits. The results are compared to the real displacementobserved in the field and conclusions are drawn about the mechanism of the landslide.

Multisegment rupture in the 11 July 1889 Chilik earthquake (Mw 8.0–8.3), Kazakh Tien Shan, interpreted from remote sensing, field survey, and paleoseismic trenching

The 11 July 1889 Chilik earthquake (M-w 8.0-8.3) forms part of a remarkable sequence of large earthquakes in the late nineteenth and early twentieth centuries in the northern Tien Shan. Despite its importance, the source of the 1889 earthquake remains unknown, though the macroseismic epicenter is sited in the Chilik valley, similar to 100 km southeast of Almaty, Kazakhstan (similar to 2 million population). Several short fault segments that have been inferred to have ruptured in 1889 are too short on their own to account for the estimated magnitude. In this paper we perform detailed surveying and trenching of the similar to 30 km long Saty fault, one of the previously inferred sources, and find that it was formed in a single earthquake within the last 700 years, involving surface slip of up to 10 m. The scarp-forming event, likely to be the 1889 earthquake, was the only surface-rupturing event for at least 5000 years and potentially for much longer. From satellite imagery we extend the mapped length of fresh scarps within the 1889 epicentral zone to a total of similar to 175 km, which we also suggest as candidate ruptures from the 1889 earthquake. The 175 km of rupture involves conjugate oblique left-lateral and right-lateral slip on three separate faults, with step overs of several kilometers between them. All three faults were essentially invisible in the Holocene geomorphology prior to the last slip. The recurrence interval between large earthquakes on any of these faults, and presumably on other faults of the Tien Shan, may be longer than the timescale over which the landscape is reset, providing a challenge for delineating sources of future hazard.

International Summer School on Rockslides and Related Phenomena in the Kokomeren River Basin, Kyrgyzstan

ICL Annual Summer School on Rockslides and Related Phenomena in Kyrgyzstan started in 2006, being supported by the IPL ProjectsM111,M126 and C106-2. This training course aims to familiarize students and young landslide researchers with various types of large-scale bedrock landslides (rockslides), with geological factors favourable for their origin and with their primary and secondary effects such as river damming and subsequent outburst floods. The Kokomeren River basin is characterised by a unique variability of rockslides that have occurred in different rock types, in confined and unconfined conditions and have formed both high dams and long-runout rock avalanches. Some of the dams remain intact while others have been deeply eroded, exposing their interiors. Particular emphasis is given on those peculiarities of rockslides’ morphology and internal structure that can clarify their motion mechanism(s) and explain the extreme mobility of rock avalanches.

Earthquakes, Landslides, Dams and Reservoirs in the Tien Shan, Central Asia

This paper presents an overview of seismic and mass movement hazards affecting major Hydropower-plants (HPP) and ongoing dam projects in the mountain regions of Central Asia. HPP cascades are located along the Naryn River in the Kyrgyz Republic and the Vakhsh-Surkhob valley fault zone in Tajikistan. The latter region hosting the presently and future tallest man-made dams of the world is very prone to earthquakes and various types of slope instabilities. The Naryn Valley hosting several dam sites is marked by the presence of ancient rockslides and a dense network of seismically active faults. In December 2009, Kyrgyz, Russian, Slovak and Belgian teams have monitored seismic ground motions and displacements induced by the blasting of a slope on the Kambarata 2 site producing a 35 m–high blockage on the Naryn River. This work is part of a NATO Science for Peace and Security project on landslide dam hazards in the Tien Shan.

International Summer School on Rockslides and Related Phenomena in the Kokomeren River Valley, Tien Shan, Kyrgyzstan: IPL-106-2 Project and WCoE

The International Summer School on Rockslides and Related Phenomena in the Kokomeren River valley, Tien Shan, Kyrgyzstan is the annual field training course focused on identification and study of large-scale bedrock landslides. These phenomena pose a threat to communities living in mountainous regions all over the world and are characterised by the enormous amount of material involved, and its high mobility and ability to create natural dams. Since 2006 more than 50 students and young landslide researchers from 17 countries have been introduced to rockslides and rock avalanches of different morphological types, some of which have formed deeply eroded rockslide dams that allow study of their internal structure, as well as evidence of inundation and of catastrophic outburst floods, and impressive manifestations of recent tectonic phenomena.

Investigating Rock-Slope Failures in the Tien Shan: State-of-the-Art and Perspectives of International Cooperation (M111)

The Tien Shan is an intracontinental mountain system ∼1 500 km long and up to 500 km wide that formed between the Tarim Basin and the Kazakh Shield due to the India-Asian collision. It is shared by the five nations of Kyrgyzstan, Kazakhstan, Uzbekistan, Tajikistan, and China. As one of the highest and most seismotectonically active parts of the Central Asian Mountain Belt, it is extremely prone to large rock-slope failures. At least nine rock slope failures > 1 km3 in volume, two of which involved ∼10 km3, have been identified in the Tien Shan. Thanks to an arid climate many of these formerly river-blocking rockslides and long-runout rock avalanches are well preserved, and both their morphology and internal structure may be readily studied in detail. Here we briefly describe the state-of-the-art and planned future international collaborations in research on rock-slope failures in the Tien Shan.