Three‐dimensional lithospheric S wave velocity model of the NE Tibetan Plateau and western North China Craton

Abstract

We present a new 3‐D lithospheric Vs model for the NE Tibetan Plateau (NETP) and the western North China Craton (NCC). First, high‐frequency receiver functions (RFs) were inverted using the neighborhood algorithm to estimate the sedimentary structure beneath each station. Then a 3D Vs model with unprecedented resolution was constructed by jointly inverting RFs and Rayleigh wave dispersions. A low‐velocity sedimentary layer with thicknesses varying from 2 to 10 km is present in the Yinchuan‐Hetao graben, Ordos block, and western Alxa block. Velocities from the middle‐lower crust to the uppermost mantle are generally high in the Ordos block and low in the Alxa block, indicating that the Alxa block is not part of the NCC. The thickened crust in southwestern Ordos block and western Alxa block suggests that they have been modified. Two crustal low‐velocity zones (LVZs) were detected beneath the Kunlun Fault (KF) zone and western Qilian Terrane (QLT). The origin of the LVZ beneath the KF zone may be the combined effect of shear heating, localized asthenosphere upwelling, and crustal radioactivity. The LVZ in the western QLT, representing an early stage of the LVZ that has developed in the KF zone, acts as a decollement to decouple the deformation between the upper and lower crust and plays a key role in seismogenesis. We propose that the crustal deformation beneath the NETP is accommodated by a combination of shear motion, thickening of the upper‐middle crust, and removal of lower crust.

Three‐Dimensional Model of the Lithospheric Structure Under the Eastern Tibetan Plateau: Implications for the Active Tectonics and Seismic Hazards

“…In general, the Moho depth is coupled with the topography in two ways: (1) higher topography corresponds to deeper Moho; lower topography, shallower Moho; and (2) higher relief corresponds to more steeply dipping Moho, whereas low‐relief surface is underlain by more shallowly dipping Moho. This observation agrees with many previous studies that are based upon Pn wave (Xu & Song, ), P wave or S wave velocity (H. Y. Li et al, ; Lei & Zhao, ; Q. Y. Liu, van der Hilst, et al, ; C. Y. Wang et al, ), passive source seismic profiling (Z. J. Zhang et al, ), wide‐angle/deep seismic reflection profiles (Guo et al, ; S. X. Jia et al, ), and receiver functions (Hu et al, , ; Shen et al, , ), as well as those crustal models that are developed using joint inversion (Laske et al, ; Lou et al, ; X. Wang, Li, et al, ) and deep seismic sounding profiles (W. Wang, Wu, et al, ).…”

“…Zhang et al, 2009), wide-angle/deep seismic reflection profiles (Guo et al, 2013; S. X. Jia et al, 2014), and receiver functions (Hu et al, , 2018Shen et al, 2011Shen et al, , 2015, as well as those crustal models that are developed using joint inversion (Laske et al, 2013;Lou et al, 2009;X. Wang, Li, et al, 2017) and deep seismic sounding profiles (W. .…”

“…Following the 2008 Wenchuan earthquake, numerous geophysical and geological surveys have provided constraints on the crustal and lithospheric structures of the eastern TP (Bai et al, ; Feng et al, ; Guo et al, ; Lei, Li, et al, ; Z. Liu et al, ; Z. Wang et al, , ; X. Wang, Li, et al, ; Wei et al, ; Z. J. Zhang et al, ). Most studies show that the Moho depth changes from ~60 km beneath the eastern TP to ~40 km beneath the SCB (Lei et al, ; H. Y. Li et al, ; Q. Y. Liu, van der Hilst, et al, ; C. Y. Wang et al, ; Xu & Song, ; P. Z. Zhang, ; Y. Q. Zhang et al, ).…”

“…Following the 2008 Wenchuan earthquake, numerous geophysical and geological surveys have provided constraints on the crustal and lithospheric structures of the eastern TP (Bai et al, 2010;Feng et al, 2016;Guo et al, 2013;Lei, Li, et al, 2014;Z. Wang et al, , 2015X. Wang, Li, et al, 2017;Wei et al, 2017;Z.…”

Seismic Tomography of Eastern Tibet: Implications for the Tibetan Plateau Growth

“…Many geophysical studies (Bao et al, ; Bao, Sun, et al, ; Fu et al, ; Jiang et al, ; Lei et al, ; J. Li et al, ; X. Liang et al, , ; Q. Y. Liu et al, ; Tian et al, ; C. Wang et al, ; X. Wang et al, ; Xu et al, ; Yao et al, , ; Yu & Chen, ; X. Zhang et al, ; Zhou & Lei, ) explored evidence supporting one or more of the aforementioned models. However, views on the development of the Tibetan Plateau are diverse and often exclusive of one another or of opposing schools of thought.…”