Late Quaternary slip rates across the central Tien Shan, Kyrgyzstan, central Asia

Abstract

[1] Slip rates across active faults and folds show that late Quaternary faulting is distributed across the central Tien Shan, not concentrated at its margins. Nearly every intermontane basin contains Neogene and Quaternary syntectonic strata deformed by Holocene north-south shortening on thrust or reverse faults. In a region that spans two thirds of the north-south width of the central Tien Shan, slip rates on eight faults in five basins range from $0.1 to $3 mm/yr. Fault slip rates are derived from faulted and folded river terraces and from trenches. Radiocarbon, optically stimulated luminescence, and thermoluminescence ages limit ages of terraces and aid in their regional correlation. Monte Carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95% confidence limits. Faults in basins appear to merge at relatively shallow depths with crustal-scale ramps that underlie mountain ranges composed of pre-Cenozoic rocks. The sum and overall pattern of late Quaternary rates of shortening are similar to current rates of north-south shortening measured using Global Positioning System geodesy. This similarity suggests that deformation is concentrated along major fault zones near range-basin margins. Such faults, separated by rigid blocks, accommodate most of the shortening in the upper crust.

Irregular earthquake cycle along the southern Tianshan front, Aksu area, China

“…The Tianshan extends laterally over $2000 km with active thrusting occurring on both sides and within the belt [Avouac et al, 1993;Burbank et al, 1999;Burchfiel et al, 1999;Thompson et al, 2002]. Along the central southern Tianshan, deformation has propagated into the Tarim basin except in the Aksu reentrant (Figure 1a), where a drastic change in stratigraphy occurs.…”

Seismic Hazard in Tien Shan: Basement Structure Control Over the Deformation Induced by Indo-Eurasia Collision

“…However in most cases, it is safe to say that cooling initiated, seemingly in a somewhat poly-phased fashion, during the last 10 to 15 Ma. These cooling curves in the models might thus represent the timing of the denudation of the modern Tien Shan orogenic edifice and can be corroborated by several lines of independent geological evidence from such fields as sedimentology [Cobbold et al, 1994;Métivier & Gaudemer, 1997;Dill et al, 2007], magneto-stratigraphy [Sun et al, 2004;Charreau et al, 2005;Huang et al, 2006;Ji et al, 2008], geomorphology and structure [Tibaldi et al, 1997;Yin et al, 1998;Burbank et al, 1999;Abdrakhmatov et al, 2001;Thompson et al, 2002;Buslov et al, 2003;Fu et al, 2003;Hubert-Ferrari et al, 2007;Oskin & Burbank, 2007], geophysics [Trapeznikov et al, 1997;Bielinski et al, 2003;Rybin et al, 2004;, geodesy [Abdrakhmatov et al, 1996;Reigber et al, 2001;Vinnik et al, 2004;Tychkov et al, 2008], and other geochronological studies [Sobel & Dumitru, 1997;Bullen et al, 2001;Sobel et al, 2006;De Grave et al, 2007a;Heermance et al, 2007]. We should caution the reader that this Late Cenozoic feature is mainly obtained by modelling the AFT data [Laslett et al, 1987;Ketcham et al, 2000].…”

Climate Evolution in Central Asia during the Past Few Million Years: A Case Study from Issyk Kul

“…Seismicity in the Tien Shan is high, with four earthquakes since 1889 assigned magnitudes as large as 8 (Abdrakhmatov et al, 2002;Kondorskaya and Shebalin, 1977). Fault plane solutions of earthquakes consistently show reverse or thrust faulting.…”

“…Moreover, some questions bear on local geology and local hazards, and all participants agreed that if a drilling program pokes holes into Kyrgyz territory, the Kyrgyz people ought to reap benefits from such a program. (Abdrakhmatov et al, 2002). The latter two events are among the largest known intracontinental earthquakes worldwide, but the recurrence intervals of such earthquakes, which could be thousands to tens of thousands of years, are still unconstrained.…”

“…Fault plane solutions of earthquakes consistently show reverse or thrust faulting. Evidence of active faulting is widespread (Abdrakhmatov et al, 2007;Chedia, 1986;Laverov and Makarov, 2005), and rates of slip on several faults exceed 1 mm yr -1 (Chen et al, 2007;Thompson et al, 2002).…”