Radial anisotropy in the crust beneath the northeastern Tibetan Plateau from ambient noise tomography

Abstract

Through analysis of Rayleigh wave and Love wave Green’s functions estimated from ambient noise tomography, we obtain radial anisotropy and shear wave velocity structure beneath the northeastern Tibetan Plateau. With two hundred and twenty three broadband seismic stations deployed by China Earthquake Administration, a collaborative seismic experiment of northern Tibet (ACSENT) experiment and northeastern Tibet seismic (NETS) experiment provide the unprecedented opportunity to resolve the spatial distribution of the radial anisotropy within the crust of the northeastern Tibetan Plateau. Discrepancies between Love (sh) and Rayleigh (sv) wave velocities show complex anisotropic patterns associated with the dynamic processes of the collision between the Indian and Eurasian plates: (1) In the upper crust, V _sv>V _sh anisotropy is dominant throughout the study area which probably reflects fossil microcracks induced by the uplift, folding and erosion geodynamic processes; (2) in the middle crust, V _sh>V _sv observed beneath the Songpan-Ganzi terrane and the northwestern Qilian orogen correlates well with a mid-crustal low velocity zone (LVZ); (3) at depths deeper than 40 km, V _sh>V _sv is still found in the Songpan-Ganzi terrane. This anisotropy could be caused by the sub-horizontal alignment of anisotropic minerals that has followed the collision between India and Eurasia. However, the northwestern Qilian orogen is associated with V _sv>V _sh anisotropy which may be related to the vertically aligned seismic anisotropic minerals caused by the crustal thickening.

Keywords

northeastern Tibetan Plateau / ambient noise tomography / radial anisotropy

References

Bao X. W., Song X. D., Xu M. J., . Crust and Upper Mantle Structure of the North China Craton and the NE Tibetan Plateau and Its Tectonic Implications. Earth and Planetary Science Letters, 2013, 369/370: 129-137.

Bensen G. D., Ritzwoller M. H., Barmin M. P., . Processing Seismic Ambient Noise Data to Obtain Reliable Broad-Band Surface Wave Dispersion Measurements. Geophysical Journal International, 2007, 169: 1239-1260.

Chang L. J., Wang C. Y., Ding Z. F., . Seismic Anisotropy of Upper Mantle in the Northeastern Margin of the Tibetan Plateau. Chinese Journal of Geophysics, 2008, 51(2): 298-306.

Chen J. H., Liu Q. Y., Li S. C., . Crust and Upper Mantle S-Wave Velocity Structure across Northeastern Tibetan Plateau and Ordos Block. Chinese Journal Geophysics, 2005, 48(2): 333-342.

Chen Y., Badal J., Zhang Z. J. Radial Anisotropy in the Crust and Upper Mantle beneath the Qinghai-Tibet Plateau and Surrounding Regions. Journal of Asian Earth Sciences, 2009, 36: 289-302.

Chen Y., Badal J., Hu J. F. Love and Rayleigh Wave Tomography of the Qinghai-Tibet Plateau and Surrounding Areas. Pure and Applied Geophysics, 2010, 167: 1171-1203.

Cheng C., Chen L., Yao H. J., . Distinct Variations of Crustal Shear Wave Velocity Structure and Radial Anisotropy beneath the North China Craton and Tectonic Implications. Gondwana Research, 2013, 23: 25-38.

Dziewonski A., Bloch S., Landisman M. A Technique for the Analysis of Transient Seismic Signals. Bulletin of the Seismological Society of America, 1969, 59: 427-444.

Flesch L. M., Holt W. E., Silver P. G., . Constraining the Extent of Crust-Mantle Coupling in Central Asia Using GPS, Geologic, and Shear-Wave Splitting Data. Earth and Planetary Science Letters, 2005, 238: 248-268.

Ge X. H., Liu J. L. Formation and Tectonic Background of the Northern Qilian Orogenic Belt. Earth Science Frontiers, 1999, 6(4): 223-230.

Guo Z., Gao X., Wang W., . Upper-and Mid-Crustal Radial Anisotropy beneath the Central Himalaya and Southern Tibet from Seismic Ambient Noise Tomography. Geophysical Journal International, 2012, 189(2): 1169-1182.

Herrmann R. B. Some Aspects of Band-Pass Filtering of Surface Waves. Bulletin of the Seismological Society of America, 1973, 63: 663-671.

Huang H., Yao H. J., van der Hilst R. D. V. D. Radial Anisotropy in the Crust of SE Tibet and SW China from Ambient Noise Interferometry. Geophysical Research Letters, 2010, 37 21 L21310

Karplus M. S., Zhao W., Klemperer S. L., . Injection of Tibetan Crust beneath the South Qaidam Basin: Evidence from INDEPTH IV Wide-Angle Seismic Data. Journal of Geophysical Research, 2011, 116 07301

Li H. Y., Su W., Wang C. Y., . Ambient Noise Rayleigh Wave Tomography in Western Sichuan and Eastern Tibet. Earth and Planetary Science Letters, 2009, 282: 201-211.

Li H. Y., Bernardi F., Michelini A. Surface Wave Dispersion Measurements from Ambient Seismic Noise Analysis in Italy. Geophysical Journal International, 2010, 180: 1242-1252.

Li H. Y., Li S., Song X. D., . Crustal and Uppermost Mantle Velocity Structure beneath Northwestern China from Seismic Ambient Noise Tomography. Geophysical Journal International, 2012, 188: 131-143.

Liang C. T., Song X. D. A Low Velocity Belt beneath Northern and Eastern Tibetan Plateau from Pn Tomography. Geophysical Research Letters, 2006, 33 22306

Luo Y., Xu Y., Yang Y. Crustal Radial Anisotropy beneath the Dabie Orogenic Belt from Ambient Noise Tomography. Geophysical Journal International, 2013, 195(2): 1149-1164.

Niu F. L., Li J. Component Azimuths of the CEArray Stations Estimated from P-Wave Particle Motion. Earthquake Science, 2011, 24: 3-13.

Nishizawa O., Yoshino T. Seismic Velocity Anisotropy in Mica-Rich Rocks: An Inclusion Model. Geophysical Journal International, 2001, 145(1): 19-32.

Pan S. Z., Niu F. L. Large Contrasts in Crustal Structure and Composition between the Ordos Plateau and the NE Tibetan Plateau from Receiver Function Analysis. Earth and Planetary Science Letters, 2011, 303: 291-298.

Pei S. P., Zhao J. M., Sun Y. S., . Upper Mantle Seismic Velocities and Anisotropy in China Determined through Pn and Sn Tomography. Journal of Geophysical Research, 2007, 112 05312

Peng Y. J., Huang Z. X., Su W., . Anisotropy in Crust and Upper Mantle beneath China Continent and Its Adjacent Seas. Chinese Journal of Geophysics, 2007, 50(3): 752-759.

Shapiro N. M., Ritzwoller M. H., Molnar P., . Thining and Flow of Tibetan Crust Constrained by Seismic Anisotropy. Science, 2004, 305(5681): 233-236.

Wang, C. Y., Han, W. B., Wu, J. P., et al., 2007. Crustal Structure beneath the Eastern Margin of the Tibetan Plateau and Its Tectonic Implications. Journal of Geophysical Research, 112: B07307. doi:10.1029/2005JB003873

Wang Q., Chung S. L., Li X. H., . Crustal Melting and Flow beneath Northern Tibet: Evidence from Mid-Miocene to Quaternary strongly Peraluminous Rhyolites in the Southern Kunlun Range. Journal of Petrology, 2012, 53(12): 2523-2566.

Wang X. B., Zhu Y. T., Zhao X. K., . Deep Conductivity Characteristics of the Longmen Shan, Eastern Qinghai-Tibet Plateau. Chinese Journal of Geophysics, 2009, 52(2): 564-571.

Wang Y. Heat Flow Pattern and Lateral Variations of Lithosphere Strength in China Mainland: Constraints on Active Deformation. Physics of the Earth and Planetary Interiors, 2001, 126(3–4): 121-146.

Weiss T., Siegesmund S., Rabbel W., . Seismic Velocities and Anisotropy of the Lower Continental Crust: A Review. Pure and Applied Geophysics, 1999, 156: 97-122.

Xu Y., Liu F. T., Liu J. H., . Seismic Tomography beneath the Northwestern China Orogen and Adjacent Basins. Science in China Series D: Earth Sciences, 2000, 30(2): 113-122.

Yang Y. J., Ritzwoller M. H., Zheng Y., . A Synoptic View of the Distribution and Connectivity of the Mid-Crustal Low Velocity Zone beneath Tibet. Journal of Geophysical Research, 2012, 117 04303

Yanovskaya T. B., Kizima E. S., Antonova L. M. Structure of the Crust in the Black Sea and Adjoining Regions from Surface Wave Data. Journal of Seismology, 1998, 2(4): 303-316.

Yue, H., Chen, J., Sandvol, E., et al., 2012. Lithospheric and Upper Mantle Structure of the Northeastern Tibetan Plateau. Journal of Geophysical Research, 117: B05307. doi:10.1029/2011JB008545