Seismicity and fault plane solutions of intermediate depth earthquakes in the Pamir‐Hindu Kush Region

Roecker, S. W.; Soboleva, O.V.; Nersesov, I. L.; Lukk, A. A.; Hatzfeld, Denis; Chatelain, Jean‐Luc; Molnár, Péter

doi:10.1029/jb085ib03p01358

Cited by 59 publications

(42 citation statements)

References 11 publications

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“…It may be divided into the upper part and the lower part, between which there is an obvious seismic gap mentioned by Roecker et al (1980) and Lou et al (2007). The upper part has smaller dip angle and the seismicity is less active.…”

Section: Resultsmentioning

confidence: 98%

“…Figure 2 shows the epicenters of the relocated earthquakes in the Pamir-Hindu Kush region color-coded by focal depth. A well-known feature pointed out by previous authors (e.g., Roecker et al, 1980;Chatelain et al, 1980;Ning and Zang, 1990;Lou et al, 2007), the S-shaped, 700 km long intermediate-depth seismic zone with few shallow events occurred above them, is further exhibited. The seismic zone has an obvious overturning change of dip direction near 36.8°N.…”

Section: Data Processing and The Applicability Of The Hypodd Programmentioning

confidence: 86%

“…Since then, a number of seismological studies for this region have been carried out (e.g. Nowroozi, 1971;Billington et al, 1977;Vinnik et al, 1977;Chatelain et al, 1980;Roecker et al, 1980;Roecker, 1982;Fan et al, 1994;Ning and Zang, 1990;Mellors et al, 1995;Zhu et al, 1997;Pegler and Das, 1998;Liu, 1999;Pavlis and Das, 2000;Lou et al, 2007). An S-shaped intermediate-depth seismic zone in this region was identified, including two segments with obviously different strikes and dip directions.…”

Section: Introductionmentioning

confidence: 99%

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Intermediate-depth earthquakes beneath the Pamir-Hindu Kush region: Evidence for collision between two opposite subduction zones

Lou

Cai

et al. 2009

Earthq Sci

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We employed a double-difference algorithm (hypoDD) to relocate earthquakes within the region bounded by 66°E−78°E and 32°N−42°N in the period of 1964−2003 reported by the International Seismological Center (ISC). The improved hypocentral locations delineate a double-layered Wadati-Benioff zone in the eastern Hindu Kush intermediate seismic belt. Based on this feature and other evidences, we propose that the intermediate-depth earthquakes beneath the Pamir-Hindu Kush region may occur in two collided subduction zones with opposite dip directions.

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Section: Resultsmentioning

confidence: 98%

Section: Data Processing and The Applicability Of The Hypodd Programmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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Intermediate-depth earthquakes beneath the Pamir-Hindu Kush region: Evidence for collision between two opposite subduction zones

Lou

Cai

et al. 2009

Earthq Sci

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“…1C; Hamburger et al, 1992;Leith and Alvarez, 1985;Thomas et al, 1994aThomas et al, , b, 1996. Seismicity suggested active intra-continental subduction along Hindu-Kush and the Pamir front (Billington et al, 1977;Chatelain et al, 1980;Negredo et al, 2007;Roecker et al, 1980). Bourgeois et al (1997) restored deformation pattern within the Tajik basin, suggesting a rotated indenter whereas Leith and Alvarez (1985) suggest that the Tajik FTB is pressed against the slope of the Gissar Range.…”

Section: Comparison Of Experimental Results With the Tajik Foldand-thmentioning

confidence: 99%

The interaction of two indenters in analogue experiments and implications for curved fold-and-thrust belts

Reiter

Kukowski

Ratschbacher

2011

Earth and Planetary Science Letters

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Editor: Y. Ricard Keywords:4D analogue experiments two indenter tectonics particle image velocimetry fold-and-thrust belts Tajik basin Pamir Scaled analogue experiments are used to investigate the indentation of two basement blocks into a sedimentary basin and the formation of a fold-and-thrust belt. The experimental set-up has two adjacent indenters moving in parallel with a velocity difference. The slow indenter moves with a relative velocity ranging from 40 to 80% of that of the fast one. In a first experimental series, quartz sand and low-friction glass beads represent the sediment stack and its basal detachment, respectively; silicone oil simulates a viscous detachment in the second series of experiments. The surface evolution and the spatio-temporal strain distribution are derived from particle image velocimetry (PIV). Together with the 3D finite structure derived by cutting the models at the end of each experiment, this allows the analysis of the structural evolution of the experimental wedges. Thrusting wedge development depends crucially on the relative velocity: when the slow indenter moves with a velocity of more than 55% of the fast indenter, a single curved thrust wedge develops. The wedge becomes decoupled along strike-slip zone at large velocity differences, i.e. when the slow indenter moves slower than 55% of the faster indenter. Consequently the thrust front is strongly curved at high (55-60%) and smoothly curved at low velocity differences (70-80%); in all cases curvature increases during indentation. Along the most strongly curved portion of the thrust wedge, the transfer zone rises, particle rotation and material transport oblique to the indentation direction occur directed toward the front of the slow indenter. Thrusting cycles are timed by the fast indenter and influence thrusting in front of the slow indenter. Thrusts nucleate in front of the fast indenter wedge and propagate laterally to the slow indenter front. This implies distant effects of wedge growth active hundreds of kilometers along-strike of orogens. Silicone oil as a detachment induces a low-angle wedge, which is less curved than in the glass beads experiments, and shows variable thrust vergence with fore-and back-thrusts. We compare our experimental results with the curved fold-and-thrust belts of the Tajik basin in front of the Hindu-Kush and Pamir indenters; our results are able to explain several first-order features.

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“…Nevertheless, Vinnik et al (1977) insisted that the intermediate-depth earthquakes represented a single active zone considering possible coupling of the earthquake zones at depth, and the occurrence of Precambrian rock outcrops in the region. The presence of two subduction zones was also concluded from later studies of micro-earthquakes in the area (Chaterlain et al, 1980;Roecker et al, 1980). Subsequent geophysical studies were inclined to support the existence of oppositely directed subductions under the Hindu Kush and Pamir (Hamburger et al, 1992;Burtman and Molnar, 1993;Fan et al, 1994).…”

Section: Introductionmentioning

confidence: 91%

Seismotectonics in the Pamir: An oblique transpressional shear and south-directed deep-subduction model

Zhang

Shan

Huang

2011

Geoscience Frontiers

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The 3-D geometry of the seismicity in Hindu KushePamirewestern China region has been defined by seismic records for 1975e1999 from the National Earthquake Information Center, the U.S. Geological Survey, and over 16,000 relocated earthquakes since 1975 recorded by the Xinjiang seismic network of China. The results show that most M s 5.0 hypocenters in the area are confined to a major intracontinental seismic shear zone (MSSZ). The MSSZ, which dips southwards in Pamir has a northdipping counterpart in the Hindu Kush to the west; the two tectonic realms are separated by the sinistral Chaman transform fault of the IndiaeAsia collisional zone. We demonstrate that the MSSZ constitutes the upper boundary of a south-dipping, actively subducting Pamir continental plate. Three seismic concentrations are recognized just above the Pamir MSSZ at depths between 45e65 km, 95e120 km, and 180e220 km, suggesting different structural relationships where each occurs. Results from focal mechanism solutions in all three seismological concentrations show orientations of the principal maximum stress to be nearly horizontal in an NNWeSSE direction. The south-dipping Pamir subduction slab is wedge-shaped with a wide upper top and a narrow deeper bottom; the slab has a gentle angle of dip in the upper part and steeper dips in the lower part below an elbow depth of ca. 80e120 km. Most of the deformation related to the earthquakes occurs within the hanging wall of the subducting Pamir slab. Published geologic data and repeated GPS measurements in the Pamir document a broad supra-subduction, upper crustal zone of evolving antithetic (i.e. north-dipping) back-thrusts that contribute to northsouth crustal shortening and are responsible for exhumation of some ultrahigh-pressure rocks formed during earlier Tethyan plate convergence. An alternating occurrence in activity of Pamir and Chaman

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Seismicity and fault plane solutions of intermediate depth earthquakes in the Pamir‐Hindu Kush Region

Cited by 59 publications

References 11 publications

Intermediate-depth earthquakes beneath the Pamir-Hindu Kush region: Evidence for collision between two opposite subduction zones

Intermediate-depth earthquakes beneath the Pamir-Hindu Kush region: Evidence for collision between two opposite subduction zones

The interaction of two indenters in analogue experiments and implications for curved fold-and-thrust belts

Seismotectonics in the Pamir: An oblique transpressional shear and south-directed deep-subduction model

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