Uppermost mantle structure beneath eastern China and its surroundings from Pn and Sn tomography

Sun, Weijia

doi:10.1002/2016gl068618

Cited by 23 publications

(17 citation statements)

References 32 publications

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“…The clear reflectors at~110 km beneath stations WFD and DLD are interpreted as the LAB rather than the MLD, which is consistent with high resolution regional tomographic results in which the high-velocity lithosphere extends only to~100 km depth (e.g., Sun & Kennett, 2016b), and high values of surface heat flow exceed 80 mW/m 2 in the ENCC (He, 2015). The ENCC had a lithosphere thickness of~200 km in the Paleozoic (~480 Ma) as inferred from diamondiferous kimberlites (Figure 1) near these two stations (e.g., Zhu et al, 2011).…”

Section: Sharp Lab and Mld In The Eastsupporting

confidence: 85%

“…This difference is an indication that melts/fluids originated from the asthenosphere have infiltrated into the stable lithosphere (Figures 7a, 7c, and S2a). The uppermost mantle shows high P wavespeeds and low S wavespeeds from the Pn and Sn traveltime inversion (Sun & Kennett, 2016b), suggesting the presence of partial melt in the zone. Such metasomatic infiltration is also indicated by geochemical studies (Y.-G. Xu et al, 2005;X.…”

Section: Gradual Lat and Mld In The Westmentioning

confidence: 99%

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Sharpness of the Midlithospheric Discontinuities and Craton Evolution in North China

et al. 2020

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The lithospheric layering and evolution of Archean cratons can be effectively constrained by seismic properties. We present fine-scale lithospheric discontinuity images of the North China Craton (NCC) using the seismic daylight imaging (SDI) technique, which is also known as the autocorrelogram method. With the aid of large-scale surface-wave velocity models, the characters of autocorrelograms related to lithospheric discontinuities in the NCC are investigated. Spatial variation in discontinuity characteristics is revealed across the craton. In the modified/destroyed eastern NCC, both the midlithospheric discontinuity (MLD) and the lithosphere-asthenosphere boundary (LAB) are rather sharp (~2 km). Various dynamic processes, including juvenile underplating, asthenospheric upwelling, and corner flow induced by paleo-Pacific Plate subduction, may contribute to such sharp interfaces. In the stable western NCC, P wave reflections cannot easily reveal the LAB, suggesting a diffuse (thicker than 30 km) lithosphere-asthenosphere transition (LAT). Multiple MLDs are also found that may have arisen during craton formation and multiple phases of rejuvenation of the cratonic lithosphere as evidenced by the petrological results. The use of higher-frequency data enables us to distinguish among the lithospheric discontinuity styles and favor multiple origins of the MLDs and LAB in the cratonic lithosphere.

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Section: Sharp Lab and Mld In The Eastsupporting

confidence: 85%

Section: Gradual Lat and Mld In The Westmentioning

confidence: 99%

Sharpness of the Midlithospheric Discontinuities and Craton Evolution in North China

et al. 2020

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“…The V Pn /V Sn ratio correlates strongly with V Sn because the V Sn range is wider than the range of V Pn . For comparison, average V Pn /V Sn observed beneath eastern China is 1.8, and the maximum range is 0.1 (Sun & Kennett, ), which is larger than our result.…”

Section: Resultscontrasting

confidence: 90%

“…Due to their high frequency and propagation path, regional seismic phases are a valuable resource to map details of the uppermost mantle V P and V S structure. The Sn regional seismic wave, a guided shear wave phase, can be used to estimate not only the uppermost mantle absolute shear velocity but also the shear wave attenuation factor

Q_{Sn}^{- 1}

(Lü et al, ; Sun & Kennett, 2016).…”

Section: Introductionmentioning

confidence: 99%

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

2020

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We constructed a detailed map of the uppermost mantle seismic structure beneath the Central and Eastern United States (CEUS) using the International Seismological Centre Bulletin and seismic waveforms from USArray. Identical Pn and Sn travel time data sets were inverted to tomographically image the uppermost mantle P wave (Pn) velocity, S wave (Sn) velocity, and the velocity ratio (V Pn /V Sn ). Furthermore, we modified the two-station method in order to limit the contributions of site response and estimate the effective attenuation of Sn phase (Q −1 Sn). Lower Q values generally correspond with lower velocities in terms of both Pn and Sn wave speeds (e.g., New England and the Mississippi Embayment), but some regions, including southern Georgia, eastern South Carolina, and the New Madrid Seismic Zone, show high velocity and low Q Sn values. This can be explained by scattering attenuation of the Sn phase. To estimate the uppermost mantle temperature, a constrained grid-search algorithm was conducted using the observed V Sn , V Pn , and Q Sn with the calculated velocities of specific compositional models. The uppermost mantle temperature result shows 300-500°C beneath the northern midcontinent and 1100°C beneath New England. Although our temperature results appear to be well resolved, we found that V Pn , V Sn , and Q Sn are not enough to constrain the detailed uppermost mantle composition model. Our results highlight significant temperature heterogeneity in the uppermost mantle across the CEUS and is consistent with there not being any melt within the uppermost mantle beneath the CEUS.

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“…Nolet et al 1998;Díaz et al 2012). For instance, the stable Sichuan Basin in China has high Sn velocities (Pei et al 2007), while Sun & Kennett (2016b) found that regions around some active volcanoes show rather low Sn velocity in eastern China and its surroundings. S wave tomography of the crust and uppermost mantle in eastern China also reveals that there are magma chambers beneath the volcanoes with strong low S-wave velocity zones into the upper mantle (Sun et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Sn-wave velocity structure of the uppermost mantle beneath the Australian continent

Wei

Sun

2018

Geophysical Journal International

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We have extracted a data set of more than 5000 Sn traveltimes for source-station pairs within continental Australia, with 3-D source relocation using Pn arrivals to improve data consistency. We conduct tomographic inversion for S-wave-speed structure down to 100 km using the Fast Marching Tomography (FMTOMO) method for the whole Australian continent. We obtain a 3-D model with potential resolution of 3.0 o × 3.0 o. The new S-wave-speed model provides strong constraints on structure in a zone that was previously poorly characterized. The S velocities in the uppermost mantle are rather fast, with patterns of variation generally corresponding to those for Pn. We find strong heterogeneities of S wave speed in the uppermost mantle across the entire continent of Australia with a close relation to crustal geological features. For instance, the cratons in the western Australia usually have high S velocities (>4.70 km s −1), while the volcanic regions on the eastern margin of Australia are characterized by low S velocities (<4.40 km s −1). Exploiting an equivalent Pn inversion, we also determine the V p /V s ratios across the whole continent. We find that most of the uppermost mantle has V p /V s between 1.65 and 1.85, but with patches in central Australia and in the east with much higher V p /V s ratios. Distinctive local anomalies on the eastern margin may indicate the positions of remnants of mantle plumes.

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Uppermost mantle structure beneath eastern China and its surroundings from Pn and Sn tomography

Cited by 23 publications

References 32 publications

Sharpness of the Midlithospheric Discontinuities and Craton Evolution in North China

Sharpness of the Midlithospheric Discontinuities and Craton Evolution in North China

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

Sn-wave velocity structure of the uppermost mantle beneath the Australian continent

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