Shear velocity model for the Kyrgyz Tien Shan from joint inversion of receiver function and surface wave data

Amy Gilligan (Corresponding Author), Steven W. Roecker, Keith F. Priestley, Ceri Nunn

Research output: Contribution to journalArticle

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Abstract

The Tien Shan is the largest active intracontinental orogenic belt on Earth. To better understand the processes causing mountains to form at great distances from a plate boundary, we analyse passive source seismic data collected on 40 broad-band stations of the MANAS project (2005–2007) and 12 stations of the permanent KRNET seismic network to determine variations in crustal thickness and shear wave speed across the range. We jointly invert P- and S-wave receiver functions with surface wave observations from both earthquakes and ambient noise to reduce the ambiguity inherent in the images obtained from the techniques applied individually. Inclusion of ambient noise data improves constraints on the upper crust by allowing dispersion measurements to be made at shorter periods. Joint inversion can also reduce the ambiguity in interpretation by revealing the extent to which various features in the receiver functions are amplified or eliminated by interference from multiples. The resulting wave speed model shows a variation in crustal thickness across the range. We find that crustal velocities extend to ∼75 km beneath the Kokshaal Range, which we attribute to underthrusting of the Tarim Basin beneath the southern Tien Shan. This result supports the plate model of intracontinental convergence. Crustal thickness elsewhere beneath the range is about 50 km, including beneath the Naryn Valley in the central Tien Shan where previous studies reported a shallow Moho. This difference apparently is the result of wave speed variations in the upper crust that were not previously taken into account. Finally, a high velocity lid appears in the upper mantle of the Central and Northern part of the Tien Shan, which we interpret as a remnant of material that may have delaminated elsewhere under the range.
Original languageEnglish
Pages (from-to)480-498
Number of pages19
JournalGeophysical Journal International
Volume199
Issue number1
Early online date16 Aug 2014
DOIs
Publication statusPublished - 1 Oct 2014

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crustal thickness
Surface waves
surface wave
surface waves
ambient noise
receivers
wave functions
inversions
shear
upper crust
S-wave
Shear waves
ambiguity
S waves
crusts
Moho
plate boundary
orogenic belt
stations
P-wave

Keywords

  • Asia
  • Continental tectonics: compressional
  • Crustal structure
  • Intra-plate processes
  • Surface waves and free oscillations
  • Tomography

Cite this

Shear velocity model for the Kyrgyz Tien Shan from joint inversion of receiver function and surface wave data. / Gilligan, Amy (Corresponding Author); Roecker, Steven W.; Priestley, Keith F.; Nunn, Ceri.

In: Geophysical Journal International, Vol. 199, No. 1, 01.10.2014, p. 480-498.

Research output: Contribution to journalArticle

Gilligan, Amy ; Roecker, Steven W. ; Priestley, Keith F. ; Nunn, Ceri. / Shear velocity model for the Kyrgyz Tien Shan from joint inversion of receiver function and surface wave data. In: Geophysical Journal International. 2014 ; Vol. 199, No. 1. pp. 480-498.
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abstract = "The Tien Shan is the largest active intracontinental orogenic belt on Earth. To better understand the processes causing mountains to form at great distances from a plate boundary, we analyse passive source seismic data collected on 40 broad-band stations of the MANAS project (2005–2007) and 12 stations of the permanent KRNET seismic network to determine variations in crustal thickness and shear wave speed across the range. We jointly invert P- and S-wave receiver functions with surface wave observations from both earthquakes and ambient noise to reduce the ambiguity inherent in the images obtained from the techniques applied individually. Inclusion of ambient noise data improves constraints on the upper crust by allowing dispersion measurements to be made at shorter periods. Joint inversion can also reduce the ambiguity in interpretation by revealing the extent to which various features in the receiver functions are amplified or eliminated by interference from multiples. The resulting wave speed model shows a variation in crustal thickness across the range. We find that crustal velocities extend to ∼75 km beneath the Kokshaal Range, which we attribute to underthrusting of the Tarim Basin beneath the southern Tien Shan. This result supports the plate model of intracontinental convergence. Crustal thickness elsewhere beneath the range is about 50 km, including beneath the Naryn Valley in the central Tien Shan where previous studies reported a shallow Moho. This difference apparently is the result of wave speed variations in the upper crust that were not previously taken into account. Finally, a high velocity lid appears in the upper mantle of the Central and Northern part of the Tien Shan, which we interpret as a remnant of material that may have delaminated elsewhere under the range.",
keywords = "Asia, Continental tectonics: compressional, Crustal structure, Intra-plate processes, Surface waves and free oscillations, Tomography",
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note = "The collection and archiving of the data used in this study was supported by the IRIS PASSCAL and DMS programs and by the NSF Continental Dynamics Project EAR 0309927. Amy Gilligan is supported by a NERC studentship, with CASE funding from Weston Geophysical. Figures were prepared using Generic Mapping Tools (GMT) software (Wessel & Smith 1998). We thank two anonymous reviewers for their comments.",
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N1 - The collection and archiving of the data used in this study was supported by the IRIS PASSCAL and DMS programs and by the NSF Continental Dynamics Project EAR 0309927. Amy Gilligan is supported by a NERC studentship, with CASE funding from Weston Geophysical. Figures were prepared using Generic Mapping Tools (GMT) software (Wessel & Smith 1998). We thank two anonymous reviewers for their comments.

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N2 - The Tien Shan is the largest active intracontinental orogenic belt on Earth. To better understand the processes causing mountains to form at great distances from a plate boundary, we analyse passive source seismic data collected on 40 broad-band stations of the MANAS project (2005–2007) and 12 stations of the permanent KRNET seismic network to determine variations in crustal thickness and shear wave speed across the range. We jointly invert P- and S-wave receiver functions with surface wave observations from both earthquakes and ambient noise to reduce the ambiguity inherent in the images obtained from the techniques applied individually. Inclusion of ambient noise data improves constraints on the upper crust by allowing dispersion measurements to be made at shorter periods. Joint inversion can also reduce the ambiguity in interpretation by revealing the extent to which various features in the receiver functions are amplified or eliminated by interference from multiples. The resulting wave speed model shows a variation in crustal thickness across the range. We find that crustal velocities extend to ∼75 km beneath the Kokshaal Range, which we attribute to underthrusting of the Tarim Basin beneath the southern Tien Shan. This result supports the plate model of intracontinental convergence. Crustal thickness elsewhere beneath the range is about 50 km, including beneath the Naryn Valley in the central Tien Shan where previous studies reported a shallow Moho. This difference apparently is the result of wave speed variations in the upper crust that were not previously taken into account. Finally, a high velocity lid appears in the upper mantle of the Central and Northern part of the Tien Shan, which we interpret as a remnant of material that may have delaminated elsewhere under the range.

AB - The Tien Shan is the largest active intracontinental orogenic belt on Earth. To better understand the processes causing mountains to form at great distances from a plate boundary, we analyse passive source seismic data collected on 40 broad-band stations of the MANAS project (2005–2007) and 12 stations of the permanent KRNET seismic network to determine variations in crustal thickness and shear wave speed across the range. We jointly invert P- and S-wave receiver functions with surface wave observations from both earthquakes and ambient noise to reduce the ambiguity inherent in the images obtained from the techniques applied individually. Inclusion of ambient noise data improves constraints on the upper crust by allowing dispersion measurements to be made at shorter periods. Joint inversion can also reduce the ambiguity in interpretation by revealing the extent to which various features in the receiver functions are amplified or eliminated by interference from multiples. The resulting wave speed model shows a variation in crustal thickness across the range. We find that crustal velocities extend to ∼75 km beneath the Kokshaal Range, which we attribute to underthrusting of the Tarim Basin beneath the southern Tien Shan. This result supports the plate model of intracontinental convergence. Crustal thickness elsewhere beneath the range is about 50 km, including beneath the Naryn Valley in the central Tien Shan where previous studies reported a shallow Moho. This difference apparently is the result of wave speed variations in the upper crust that were not previously taken into account. Finally, a high velocity lid appears in the upper mantle of the Central and Northern part of the Tien Shan, which we interpret as a remnant of material that may have delaminated elsewhere under the range.

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KW - Intra-plate processes

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