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Multiparameter adjoint tomography of the crust and upper mantle beneath East Asia: 1. Model construction and comparisons

Author(s): Chen, Min; Niu, Fenglin; Liu, Qinya; Tromp, Jeroen; Zheng, Xiufen

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 Abstract: We present a 3‐D radially anisotropic model of the crust and mantle beneath East Asia down to 900 km depth. Adjoint tomography based on a spectral element method is applied to a phenomenal data set comprising 1.7 million frequency‐dependent traveltime measurements from waveforms of 227 earthquakes recorded by 1869 stations. Compressional wave speeds are independently constrained and simultaneously inverted along with shear wave speeds (VSH and VSV) using the same waveform data set with comparable resolution. After 20 iterations, the new model (named EARA2014) exhibits sharp and detailed wave speed anomalies with improved correlations with surface tectonic units compared to previous models. In the upper 100 km, high wave speed (high‐V) anomalies correlate very well with the Junggar and Tarim Basins, the Ordos Block, and the Yangtze Platform, while strong low wave speed (low‐V) anomalies coincide with the Qiangtang Block, the Songpan Ganzi Fold Belt, the Chuandian Block, the Altay‐Sayan Mountain Range, and the back‐arc basins along the Pacific and Philippine Sea Plate margins. At greater depths, narrow high‐V anomalies correspond to major subduction zones and broad high‐V anomalies to cratonic roots in the upper mantle and fragmented slabs in the mantle transition zone. In particular, EARA2014 reveals a strong high‐V structure beneath Tibet, appearing below 100 km depth and extending to the bottom of the mantle transition zone, and laterally spanning across the Lhasa and Qiangtang Blocks. In this paper we emphasize technical aspects of the model construction and provide a general discussion through comparisons. Publication Date: 31-Jan-2015 Citation: Chen, Min, Fenglin Niu, Qinya Liu, Jeroen Tromp, and Xiufen Zheng. "Multiparameter adjoint tomography of the crust and upper mantle beneath East Asia: 1. Model construction and comparisons." Journal of Geophysical Research: Solid Earth 120, no. 3 (2015): 1762-1786. doi:10.1002/2014JB011638. DOI: doi:10.1002/2014JB011638 ISSN: 2169-9313 EISSN: 2169-9356 Pages: 1762 - 1786 Type of Material: Journal Article Journal/Proceeding Title: Journal of Geophysical Research: Solid Earth Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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