Evidence for strong paleoearthquakes along the Talas-Fergana Fault near the Kök-Bel Pass, Kyrgyzstan

Korjenkov, A.M.; Bobrovskii, A. V.; Mamyrov, E.

doi:10.1134/s0016852110030040

Cited by 21 publications

(21 citation statements)

References 2 publications

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“…Paleosoils of calibrated ages from 2340 ± 120 years (calibrated 800 BC to 100 BC with a probability of 95.4%) to 4900 ± 230 years (calibrated 4300 BC to 3000 BC with a probability of 95.4%) were found in dry valley sections near the Kokbel Pass (V-9 in Fig. 10) [58,59]. Perhaps, these dates characterize the age of the offset landforms.…”

Section: The Talas-fergana Fault In Tian Shanmentioning

confidence: 95%

“…The deposits in the Karakulja River source to the NW of the Karakulja Pass (the central part of segment VI) gave dates of 1523e1800 [60]. Several 14 C dates were obtained in segment V near the Kokbel Pass [58] and in the upper Karasu River [57]. The majority of the dates demonstrated a dispersion of values from the XVI century to the XVIII century, yet according to the most accurate data, the most probable age of this strong paleoseismic event (Kokbel earthquake) is 1526e1633 (Table 5, Figs.…”

Section: The Talas-fergana Fault In Tian Shanmentioning

confidence: 99%

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Recent geodynamics of major strike-slip zones

Трифонов

Корженков

Omar

2015

Geodesy and Geodynamics

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Active strike-slip faults Historical seismicity Paleoseismicity Temporal variations of focal mechanisms of earthquakes Rates of accumulation of strike-slip deformation a b s t r a c t The subject of this study is strike-slip fault zones, where temporal variations of accumulation in strike-slip deformation complicate the standard process of deformation accumulation and release during strong earthquakes. These temporal variations are expressed in the El Ghab segment of the Dead Sea Transform zone (DST, Eastern Mediterranean) and in the Talas-Fergana fault zone (Central Asia). According to Global Positioning System (GPS)data, the strike-slip deformations within these zones are not now accumulating or are accumulating at a rate that is significantly less than their average rate during the Holocene and Quaternary or the PlioceneeQuaternary. Simultaneously, weak transverse shortening has been measured in both zones by GPS. In both of these zones, strong earthquakes have not registered within the XX century, yet epochs of intensified seismicity (strong earthquakes) took place throughout history. In the southern and central parts of the El Ghab zone, there is evidence of 30 strong historical earthquakes of Ms ! 5.7; however, no instrumental earthquakes of Ms ! 5 have been identified. The temporal distribution of seismic energy released by these earthquakes demonstrates a 350 ± 50-year cycle. Values for the seismic energies released during the peak phases of these cycles are approximated by a sinusoid that suggests the possibility of a !1800-year cycle ("hyper-cycle"), which began around the 3rd century, reached its maximum in the 12th century, and has continued until now. A combination of geological, archaeoseismological, and geodetic data show that the rate of sinistral strike-slip deformation varied in the fault zone, probably in conformity with the variation of seismicity during the "hyper-cycle." In the Talas-Fergana fault zone, trenching and 14 C dating that was correlated with right lateral offsets, gave a possible preliminary estimate of the average rates of the Late Holocene strike slip of about 10 mm per year, with a decrease in the SE direction to 4 mme4.5 mm per year. These studies also showed that the slip in the Talas-Fergana fault zone was realized mainly during strong earthquakes. New trenching and 14 C dating of paleoearthquake records identified the epoch of seismicity intensification dating to the XIVeXVII centuries. These paleoearthquakes could produce a total dextral slip at several meters. Therefore, consideration of these epochs was necessary to determine a calculated average slip rate during the Late Holocene.The main shock and the strongest aftershocks of the Altai earthquake of September 27, 2003, with Ms ¼ 7.0 demonstrated a strike-slip focal mechanism with an NW-trending

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Section: The Talas-fergana Fault In Tian Shanmentioning

confidence: 95%

Section: The Talas-fergana Fault In Tian Shanmentioning

confidence: 99%

Recent geodynamics of major strike-slip zones

Трифонов

Корженков

Omar

2015

Geodesy and Geodynamics

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“…Our field surveys revealed a slope dip range from 35°-40° and a geometry compatible with circular failure mechanisms. The age of these landslides is unknown, but based on available 14 C dating (SOAN-7026 240±50 yr, in Korjenkov et al, 2010;Korjenkov et al, 2012), they are more recent than 240-370 ys BP. The lithological and stratigraphic characterization of the soils involved in Type 1 shallow instabilities close to the Kokbel' Pass area (Fig.…”

Section: Type 1 Instabilities In the Kokbel' Pass Areamentioning

confidence: 98%

Tectonic and gravity-induced deformation along the active Talas–Fergana Fault, Tien Shan, Kyrgyzstan

et al. 2015

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“…that acceleration values are not higher along this fault zone than for the surrounding area if the shorter standard return period of 475 years is considered (due to the large time intervals of several hundreds of years between characteristic major shocks occurring on each of the three segments of this fault, see Korjenkov et al 2010). Here, the extreme PGA values for large return periods were not used for the seismic dam stability assessment as those values are affected by very high uncertainty; further, it will be shown that dam instability becomes critical even for the 475-year PGA values.…”

Section: Introductionmentioning

confidence: 98%

The Kambarata 2 blast-fill dam, Kyrgyz Republic:blast event, geophysical monitoring and dam structure modelling

Havenith

Torgoev²,

Torgoev

et al. 2015

GEOENVIRON DISASTERS

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Background: The blast-and earth-fill dam of the Kambarata 2 hydropower station is situated in the seismically active Central Tien Shan region of the Kyrgyz Republic. More than 70% of the dam volume was produced during a blast event on December 22, 2009. In 2010-2011, dam construction was completed after earth filling on top of the blasted material and installing concrete and clay screens together with bentonite grouts. A geophysical survey had been completed in 2012-2013, mainly to monitor the resistivities inside the dam. Results: The geophysical survey completed on the Kambarata 2 dam site showed lower resistivity zones in the earth fill and relatively higher resistivities in the blast-fill material. Topographic, geophysical and piezometric inputs had been compiled within a 3D geomodel constructed with GOCAD software. This model was compared with the design structure of the dam in order to define the upper limits of the underlying alluvium, the deposited blast fill, earth fill and top gravel materials (represented by the dam surface). The central cross-section of this model was extrapolated over the full length of the main dam profile. Conclusions: On the basis of a calibrated hydrogeological model and known geomechanical properties of the materials, dam stability calculations were completed for different scenarios considering different reservoir levels and varying seismic conditions. Some of these scenarios indicated a critical vulnerability of the dam, e.g., if impacted by a horizontal seismic acceleration of Ah = 0.3 g and a vertical seismic acceleration Av = 0.15 g, with an estimated return period of 475 years. As a general conclusion, it was noted that this case study can be used as an example for surveys on much larger natural -landslide or moraine -dams. A series of geophysical methods (e.g., electrical and electro-magnetic techniques, seismic and microseismic measurements) can be applied to investigate even very deep dam structures. These methods have the advantage over classical direct prospecting techniques, such as drilling, of using equipment that is much lighter and thus more easily transportable and applicable in difficult terrain. Furthermore, they can provide continuous information over wider areas. This specific application to a blast-fill dam allows us to better outline the strengths and weaknesses of the exploration types and geomodels as a series of investigated parameters can be verified more easily than for natural dams.

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Evidence for strong paleoearthquakes along the Talas-Fergana Fault near the Kök-Bel Pass, Kyrgyzstan

Cited by 21 publications

References 2 publications

Recent geodynamics of major strike-slip zones

Recent geodynamics of major strike-slip zones

Tectonic and gravity-induced deformation along the active Talas–Fergana Fault, Tien Shan, Kyrgyzstan

The Kambarata 2 blast-fill dam, Kyrgyz Republic:blast event, geophysical monitoring and dam structure modelling

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