Lithospheric Structure Across the Alaskan Cordillera From the Joint Inversion of Surface Waves and Receiver Functions
Lithospheric Structure Across the Alaskan Cordillera From the Joint Inversion of Surface Waves and Receiver Functions
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DOI：
10.1029/2018jb015967
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发表时间：
2018-10
期刊：
影响因子：
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通讯作者：
K. Ward;F. Lin
中科院分区：
文献类型：
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作者：
K. Ward;F. Lin
USArray 可移动阵列的最后部署阶段已接近完成，北美科迪勒拉山脉几年来的高质量宽带地震数据已经公开。科迪勒拉山脉的这一段代表了构造变形和增生事件的丰富历史以及众多活跃的构造过程。许多活跃的构造过程，例如隆升机制或岩浆系统，都是通过区域或有限的二维研究中成像的结构来解释的。为了研究地壳和最上地幔（<70 km）的完整 3D 性质，我们提出了阿拉斯加科迪勒拉剪切波速度结构的联合接收函数、表面波反演的结果。我们新的各向同性速度模型与现有数据集（包括地震活动、重力异常和其他地震成像方法）的集成表明，我们的速度模型与以前的研究一致，同时提供了前所未有的额外细节。我们模型的一个突出特征是低速地幔楔。我们认为这种低速地幔楔是由俯冲板片岩石圈产生的。这种解释的构造意义在于，速度异常比板块地震活动向东延伸得更远，这表明下行板块向东延伸得更远，尽管是地震性的。这种解释为兰格尔活火山的位置提供了简单的解释。我们期望我们的速度模型将与其他地幔断层扫描模型相结合，以进一步完善我们对这种复杂构造环境的理解。
The final deployment stage of the USArray Transportable Array is nearly complete with several years of high‐quality broadband seismic data across the Northern American Cordillera already publicly available. This section of the Cordillera represents a rich history of tectonic deformation and accretion events as well numerous active tectonic processes. Many of these active tectonic processes such as uplift mechanisms or magmatic systems have been interpreted from structures imaged in regional or limited 2‐D studies. To investigate the fully 3‐D nature of the crust and uppermost mantle (<70 km), we present the results of a joint receiver function, surface wave inversion for the shear wave velocity structure across the Alaskan Cordillera. Integration of our new isotropic velocity model with existing data sets, including seismicity, gravity anomalies, and other seismic imagining methods, indicates that our velocity model is consistent with previous studies while providing unprecedented additional detail. A prominent feature in our model is a low‐velocity mantle wedge. We suggest this low‐velocity mantle wedge results from subducting slab lithosphere. The tectonic significance of this interpretation is that the velocity anomaly extends further to the east than slab seismicity does, suggesting that the downgoing slab extends further to the east, albeit aseismicly. This interpretation provides a simple explanation for the location of the active Wrangell volcanoes. We expect that our velocity model will be integrated with other mantle tomography models to further refine our understanding of this complex tectonic setting.