Crustal azimuthal anisotropy beneath the central North China Craton revealed by receiver functions.
Crustal azimuthal anisotropy beneath the central North China Craton revealed by receiver functions.
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接收函数揭示的华北克拉通中部地壳方位各向异性.
DOI：
10.1029/2019gc008181
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Fan Xiaoping
中科院分区：
文献类型：
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作者：
Zheng Tuo;Ding Zhifeng;Ning Jieyuan;Liu H. Kelly;Gao S. Stephen;Chang Lijun;Kong Fansheng;Fan Xiaoping
为了表征华北中部地区地壳各向异性特征，我们采用一种新的反褶积方法，有效地去除了200个宽带地震台站记录的接收函数中的近地表反射，并通过拟合来自莫霍面和壳内不连续面的PtoS转换相位的正弦时差，确定了地壳方位各向异性的快速方向和大小。地壳各向异性的大小范围为0.06 s ~ 0.54 s，平均值为0.25 ± 0.08 s。地震活跃的张家口-蓬莱断裂带中的断层平行各向异性是显著的，并且可能与流体填充的裂缝有关。历史强震主要发生在地壳各向异性显著的断裂带段，说明实测地壳各向异性与地壳形变程度密切相关。观测到的地壳各向异性的空间分布表明，断裂带的西北端可能终止于114°E左右。此外，还观察到被南北重力线分隔的燕山隆起的西部和东部在快速方向上的鲜明对比。燕山西部的NW-SE向各向异性是由于CNCC岩石圈伸展引起的“化石”地壳各向异性，而燕山东部的ENE-WSW向各向异性是由区域压应力引起的伸展流体饱和微裂纹引起的。地壳各向异性测量值与先前确定的上地幔各向异性的比较表明，CNCC的壳幔耦合程度在空间上是变化的。
To characterize crustal anisotropy beneath the central North China Craton (CNCC), we apply a recently developed deconvolution approach to effectively remove near‐surface reverberations in the receiver functions recorded at 200 broadband seismic stations and subsequently determine the fast orientation and the magnitude of crustal azimuthal anisotropy by fitting the sinusoidal moveout of thePtoSconverted phases from the Moho and intracrustal discontinuities. The magnitude of crustal anisotropy is found to range from 0.06 s to 0.54 s, with an average of 0.25 ± 0.08 s. Fault‐parallel anisotropy in the seismically active Zhangjiakou‐Penglai Fault Zone is significant and could be related to fluid‐filled fractures. Historical strong earthquakes mainly occurred in the fault zone segments with significant crustal anisotropy, suggesting that the measured crustal anisotropy is closely related to the degree of crustal deformation. The observed spatial distribution of crustal anisotropy suggests that the northwestern terminus of the fault zone probably ends at about 114°E. Also observed is a sharp contrast in the fast orientations between the western and eastern Yanshan Uplifts separated by the North‐South Gravity Lineament. The NW‐SE trending anisotropy in the western Yanshan Uplift is attributable to “fossil” crustal anisotropy due to lithospheric extension of the CNCC, while extensional fluid‐saturated microcracks induced by regional compressive stress are responsible for the observed ENE‐WSW trending anisotropy in the eastern Yanshan Uplift. Comparison of crustal anisotropy measurements and previously determined upper mantle anisotropy implies that the degree of crust‐mantle coupling in the CNCC varies spatially.