2018 International Summer School on rockslides and related phenomena in the Kokomeren River valley (Kyrgyzstan)

Information about the next Kokomeren Summer School that will take place on August 15–30, 2018, is provided.     

OSL dating of glacial deposits during the Last Glacial in the Terskey-Alatoo Range, Kyrgyz Republic

Optically stimulated luminescence (OSL) dating was applied to glacial and loess deposits in the north flank of the Terskey-Alatoo Range, Kyrgyz Republic, to elucidate the glacier chronology of the central Asian mountains during the Last Glacial. Moraines in five parts of study area were classified into four stages (Terskey Stages I–IV) based on their geographical position and elevation, and their moraine rock weathering. According to this classification, the oldest moraines (Terskey Stage I) were at 2100–2250 m a.s.l. and the second-oldest moraines (Terskey Stage II) were at 2400–2700 m a.s.l. Quartz samples from moraines of these two stages were used for OSL dating. The OSL ages of the quartz samples indicate that glacier expansion in the Terskey Stage II occurred between 21 and 29 ka BP.     

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 Janbus 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.     

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.     

Partitioning of intermontane basins by thrust-related folding, Tien Shan, Kyrgyzstan

Well-preserved, actively deforming folds in the Tien Shan of Kyrgyzstan provide a natural laboratory for the study of the evolution of thrust-related folds. The uplifted limbs of these folds comprise weakly indurated Cenozoic strata that mantle well-lithified Palaeozoic bedrock. Their contact is a regionally extensive unconformity that provides a persistent and readily traceable marker horizon. Based on the deformation of this marker, preserved fold geometries support simple geometric models for along-strike gradients in fold amplitude and displacement along the underlying faults, linkage among multiple structures, transfer of displacement among folds and evolution of the folds as geomorphic entities. Subsequent to initial uplift and warping of the unconformity surface, steeply dipping reverse faults cut the forelimbs of many of these folds. Wind gaps, water gaps, recent faulting and progressive stripping of the more readily eroded Cenozoic strata indicate the ongoing lateral propagation and vertical growth of fault-related folds. The defeat of formerly antecedent rivers coincides in several places with marked increases in erosional resistance where their incising channels first encountered Palaeozoic bedrock. Persistent dip angles on the backlimbs of folds indicate strikingly uniform geometries of the underlying faults as they propagate both laterally and vertically through the crust. Deformation switches irregularly forward and backward in both time and space among multiple active faults and folds with no systematic pattern to the migration of deformation. This distributed deformation appears characteristic of the entire Kyrgyz Tien Shan.     

Towards an improved seismic risk scenario for Bishkek,Kyrgyz Republic

A risk scenario for Bishkek, capital of the Kyrgyz Republic, is evaluated by considering a magnitude 7.5 earthquake occurring over the Issyk-Ata fault. The intensity values predicted through the application of an attenuation relationship and a recently compiled vulnerability composition model are used as inputs for seismic risk assessment, carried out using the Cedim Risk Estimation Tool (CREST) code. Although the results of this study show a reduction by as much as a factor of two with respect to the results of earlier studies, the risk scenario evaluated in this paper confirms the large number of expected injuries and fatalities in Bishkek, as well as the severe level of building damage.