Receiver function analysis of crustal structure beneath the eastern Tibetan plateau

Xu, Xiaoming; Ding, Zhongli; Shi, Dan; Li, Xinfu

doi:10.1016/j.jseaes.2013.04.018

Cited by 39 publications

(31 citation statements)

References 40 publications

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“…In general, the lower crustal ductile flow may result in the lower crust thickening. Some previous studies on the thickness and V p / V s ratio (or the Poisson's ratio) of the crust suggest that the Poisson's ratio is low in the Qilian Orogenic Belt and Western Qinling (northeastern corner of the Tibetan Plateau), which seemingly indicates that crustal thickening occurred mainly in the upper crust, being inconsistent with the lower crustal ductile flow model [e.g., Vergne et al , ; Pan and Niu , ; Tian and Zhang , ; Xu et al , , ]. These results rely on an assumption that the upper crust is felsic in composition with a lower Poisson's ratio, whereas the lower crust is mafic in composition with a higher Poisson's ratio [e.g., Tarkov and Vavakin , ; Zandt and Ammon , ; Christensen , ].…”

Section: Interpretation and Discussionmentioning

confidence: 98%

Seismic tomography and anisotropy of the Helan‐Liupan tectonic belt: Insight into lower crustal flow and seismotectonics

et al. 2016

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We determined detailed 3‐D P and S wave velocities (Vp and Vs) and Poisson's ratio (σ) images as well as P wave azimuthal anisotropy in the crust and uppermost mantle beneath the Helan‐Liupan tectonic belt (HLTB) and adjacent regions. The data set used in this study consists of 38,880 P wave and 35,117 S wave arrival times from 5028 local earthquakes recorded by 66 seismic stations in the study area during 1980 to 2014. Obvious low‐Vp and low‐σ anomalies are revealed in the lower crust beneath the Qilian Orogenic Belt and Western Qinling, which we interpret as a weakened zone mainly caused by water and capable of ductile flow on a geological timescale. Our P wave anisotropy results suggest that the flow direction in the lower crust is nearly parallel to the direction of the geodetic crustal motion and that of the upper mantle flow beneath the study region. Most of the 26 large historical earthquakes (1125–1954) in the study region occurred in the boundary zones where Vp, Vs, and σ change drastically over a short distance. Beneath the source areas of the large historical earthquakes, fluid‐related low‐velocity zones exist widely in the lower crust. The fluids result from dehydration of hydrous minerals in the deeper crust and uppermost mantle beneath the northeastern Tibetan Plateau. When the fluids migrate upward to the active faults, the fault zone friction is reduced and so large crustal earthquakes can be triggered. Our present results shed new light on the seismogenesis and geodynamics of the northeastern Tibetan Plateau and adjacent areas.

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Section: Interpretation and Discussionmentioning

confidence: 98%

Seismic tomography and anisotropy of the Helan‐Liupan tectonic belt: Insight into lower crustal flow and seismotectonics

et al. 2016

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“…In this study, I have applied a new anisotropic H‐ κ stacking technique to melt beneath the Afar Depression, but in fact this technique could constrain crustal anisotropy beneath any setting. H κ has shown evidence for high κ (>1.9) beneath transform faults [ Ozacar and Zandt , ; Ozacar et al ., ], mountain building regions [ Xu et al ., ] and other volcanic settings [ Ai et al ., ; Eagar et al ., ; Yang et al ., ]. In all these cases, melt has been invoked to explain the high values of κ .…”

Section: Discussionmentioning

confidence: 99%

Constraining melt geometries beneath the Afar Depression, Ethiopia from teleseismic receiver functions: The anisotropic H‐κstacking technique

Hammond

2014

Geochem. Geophys. Geosyst.

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Understanding the nature of the crust has long been a goal for seismologists when imaging the Earth. This is particularly true in volcanic regions where imaging melt storage and migration can have important implications for the size and nature of an eruption. Receiver functions and the H-j stacking (Hj) technique are often used to constrain crustal thickness (H) and the ratio of P to S wave velocities (j). In this paper, I show that it is essential to consider anisotropy when performing Hj. I show that in a medium with horizontally transverse isotropy a strong variation in j with back azimuth is present, which characterizes the anisotropic medium. In a vertically transverse isotropic medium, no variation in j with back azimuth is observed, but j is increased across all back azimuths. Thus, estimates of j are more difficult to relate to composition than previously thought. I extend these models to melt-induced anisotropy and show that similar patterns are observed, but with more significant variations and increases in j. Based on these observations, I develop a new anisotropic H-j stacking technique which inverts Hj data for melt fraction, aspect ratio, and orientation of melt inclusions. I apply this to data for the Afar Depression and show that melt is stored in interconnected stacked sills in the lower crust, which likely supply the recent volcanic eruptions and dike intrusions. This new technique can be applied to any anisotropic medium where it can provide constraints on the average crustal anisotropy.

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“…Many studies have investigated the crustal structure of the Sichuan basin and eastern Tibetan Plateau [e.g., Hu et al ., ; Li et al ., ; Liu et al ., ; Sun et al ., ; Wang et al ., , , Y. Wang et al , ; Wang et al , ; Xu et al ., ; Yang et al ., ; Zhang et al ., ; Xu and Song , ; Zhou et al ., ]. The results from S and P wave receiver function analysis as well as ambient noise surface wave and P wave tomography show that the crustal thickness of the Ahba subblock ranges from 50 km to 60 km northwestward.…”

Section: Regional Tectonic Settingmentioning

confidence: 99%

Geodetic imaging of potential seismogenic asperities on the Xianshuihe‐Anninghe‐Zemuhe fault system, southwest China, with a new 3‐D viscoelastic interseismic coupling model

Jiang

Chen

et al. 2015

JGR Solid Earth

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We use GPS and interferometric synthetic aperture radar (InSAR) measurements to image the spatial variation of interseismic coupling on the Xianshuihe-Anninghe-Zemuhe (XAZ) fault system. A new 3-D viscoelastic interseismic deformation model is developed to infer the rotation and strain rates of blocks, postseismic viscoelastic relaxation, and interseismic slip deficit on the fault surface discretized with triangular dislocation patches. The inversions of synthetic data show that the optimal weight ratio and smoothing factor are both 1. The successive joint inversions of geodetic data with different viscosities reveal six potential fully coupled asperities on the XAZ fault system. Among them, the potential asperity between Shimian and Mianning, which does not exist in the case of 10 19 Pa s, is confirmed by the published microearthquake depth profile.Besides, there is another potential partially coupled asperity between Daofu and Kangding with a length scale up to 140 km. All these asperity sizes are larger than the minimum resolvable wavelength. The minimum and maximum slip deficit rates near the Moxi town are 7.0 and 12.7 mm/yr, respectively. Different viscosities have little influence on the roughness of the slip deficit rate distribution and the fitting residuals, which probably suggests that our observations cannot provide a good constraint on the viscosity of the middle lower crust. The calculation of seismic moment accumulation on each segment indicates that the Songlinkou-Selaha (S4), Shimian-Mianning (S7), and Mianning-Xichang (S8) segments are very close to the rupture of characteristic earthquakes. However, the confidence level is confined by sparse near-fault observations.

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Receiver function analysis of crustal structure beneath the eastern Tibetan plateau

Cited by 39 publications

References 40 publications

Seismic tomography and anisotropy of the Helan‐Liupan tectonic belt: Insight into lower crustal flow and seismotectonics

Seismic tomography and anisotropy of the Helan‐Liupan tectonic belt: Insight into lower crustal flow and seismotectonics

Constraining melt geometries beneath the Afar Depression, Ethiopia from teleseismic receiver functions: The anisotropic H‐κstacking technique

Geodetic imaging of potential seismogenic asperities on the Xianshuihe‐Anninghe‐Zemuhe fault system, southwest China, with a new 3‐D viscoelastic interseismic coupling model

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