Nature of the intermediate seismic zone in the mantle of Pamirs—Hindu-Kush

Vinnik, Lev; Lukk, A. A.; Nersesov, I. L.

doi:10.1016/0040-1951(77)90208-6

Cited by 35 publications

(28 citation statements)

References 7 publications

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“…The stronger and thinner oceanic crust results in denser and thinner W-B zone below 200 km in the east end of the Hindu Kush zone. High velocity at depth greater than 200 km and low velocity above 200 km revealed by some tomographic images (Vinnik et al, 1977;Roecker, 1982;Hamburger, et al, 1992;Mellors et al, 1995) are consistent with the idea of transition from a continental slab to an oceanic slab. However, tomographic features showed by different authors are different and need further confirmation (Koulakov and Sobolev, 2006;Huang and Zhao, 2006) Secondly, the Harvard CMT solutions in the double-layered W-B zone in Hindu Kush does not exhibit systematic differences between the two layers (Lou et al, 2007), which further validates that the earthquake hypocenters of the double-layered W-B zone in Hindu Kush region delineate two subducting slabs.…”

Section: Resultssupporting

confidence: 86%

“…However, this model cannot clearly explain the geometrical consistency between the two seismic zones. On the other hand, the one-slab model favors a single subducting slab dipping northward, of which the Pamir part overturned at some point and formed the current two adjacent Wadati-Benioff (W-B) zones with opposite dip directions (Vinnik et al, 1977;Billington et al, 1977;Pegler and Das, 1998;Pavlis and Das, 2000). A remarkable alignment of the Pamir and the Hindu Kush seismic zones around the boundary region is the main argument for this model.…”

Section: Introductionmentioning

confidence: 88%

“…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%

“…Located at the western Himalayan syntaxis, the Pamir-Hindu Kush region is one of the most active regions of intermediate-depth earthquakes which are not obviously related to well-defined subducting slabs inspite of some geophysical evidences (e.g., Vinnik et al, 1977;Roecker, 1982;Mellors et al, 1995;Van der Voo et al, 1999;Lei and Zhao, 2002;Huang and Zhao, 2006;Negredo et al, 2007). The accurate spatial distribution of those earthquakes and their focal mechanism solutions are helpful to understanding the actual geometry as well as the stress state of possibly existing subduction zones in this region, and can provide constraints on plate interaction and tectonic evolution in the Pamir-Hindu Kush region.…”

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: Resultssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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“…Intermediate-and deep-focus earthquakes occurring in the Hindu KushePamir region are thought to result from the on-going deep subduction of continental lithosphere following continentecontinent collision along the Tethys zone (Vinnik et al, 1977(Vinnik et al, , 1978Roecker, 1982;Katok, 1988;Hamburger et al, 1992;Burtman and Molnar, 1993;Fan et al, 1994;Pegler and Das, 1998;Zhang et al, 2002). As yet, there has been no detailed study about how and why deep-subduction occurred at such a place.…”

Section: Introductionmentioning

confidence: 97%

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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Spatial Distribution of Intermediate Earthquakes and Focal Mechanism Solutions in the Pamir‐Hindu Kush Region

Lou

Gui-ling

et al. 2007

Chinese J of Geophysics

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In this paper, high quality seismic data in 1964~2003 from the ISC (International Seismological Centre) catalog are used to present a relatively more complete and definite geometric structure of the intermediate seismic zone in the Pamir‐Hindu Kush region. Dip directions and the largest depth of the Hindu Kush intermediate seismic zone (H zone) and the Pamir intermediate seismic zone (P zone) change along the strike, so they can be further divided into five segments: HW (west segment of the H zone), HE (east segment of the H zone), PSW (southwest segment of the P zone), PM (middle segment of the P zone), and PNE (northeast segment of the P zone). There is a seismic gap in the H zone at about 170~190 km depth, beneath which the seismic zone dips nearly vertically. Meanwhile, the seismic zone beneath the gap forms an inverted V‐shape zone, the two branches of which are nearly perpendicular with each other. The west branch within the HW segment does not have double seismic layers. The east branch within the HE segment is deeper and has double seismic layers. Focal mechanism solutions of the intermediate earthquakes have regular patterns. In the Hindu Kush region, most T axes are nearly vertical while most P axes are nearly horizontal and perpendicular to the strike of the seismic zone. In the Pamir region, from southwest to northeast, horizontal along‐strike axis changes from P to B and then T; P axes gradually change to be perpendicular to the strike. At last, we discuss the possible geodynamic explanations for the seismicity in this region.

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Nature of the intermediate seismic zone in the mantle of Pamirs—Hindu-Kush

Cited by 35 publications

References 7 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

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

Spatial Distribution of Intermediate Earthquakes and Focal Mechanism Solutions in the Pamir‐Hindu Kush Region

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