Collaborative Research: High Resolution Imaging of Deep Mantle Structure and Dynamics Using USArray Data

USArray可移动阵列（TA）和骨干阵列数据将用于深部地幔结构和过程的高分辨率地震分析，这些数据基于EarthScope最初5年部署的数据获得的令人兴奋的结果。亚利桑那州立大学和加州大学圣克鲁斯分校的研究人员将扩大他们的合作，分析穿越三个子区域深层地幔的远震地震信号：美国南部-墨西哥湾-中美洲-加勒比海，太平洋东部和中部，阿拉斯加和北太平洋。波形叠加、born -散射偏移、剪切波分裂和2.5D/3D波形建模程序将应用于宽带P和S到达，利用USArray数据覆盖的密度和空间孔径来解析精细尺度结构。随着TA逐渐东移，我们将特别关注中美洲和墨西哥湾的中深部地幔，在那里层析模型显示了一个通过下地幔延伸并在D区广泛传播的表格状高速结构，这被认为与法拉龙板块和北美的长期俯冲历史有关。研究人员将使用旅行时间和偏移相结合的方法来研究该特征的速度梯度、结构连续性、结构结构和空间范围，并使用2.5D和3D合成地震记录建模来量化弹性和各向异性结构。分析了阿拉斯加俯冲带深处相应的下行构造，并将两个辐合带区域与中太平洋东部构造进行了比较，其中D”区存在从化学特征明显的大低剪切速度省向相邻高速度构造的横向突变。与矿物物理学和地球动力学同事的持续合作将使我们能够探索地幔中浅层和深层结构之间的联系，以及它们对北美大陆构造和演化的动态影响。

USArray Transportable Array (TA) and Backbone Array data will be used in high-resolution seismic analyses of deep mantle structure and processes, building on exciting results obtained using data from the initial 5 years of EarthScope deployment. Arizona State University and University of California, Santa Cruz, researchers will extend their collaboration, analyzing teleseismic earthquake signals that traverse the deep mantle in three sub-regions: beneath the southern U.S.-Gulf of Mexico-Central America-Caribbean, under the eastern and central Pacific, and beneath Alaska and the northern Pacific. Waveform stacking, Born-scattering migration, shear-wave splitting and 2.5D/3D waveform modeling procedures will be applied to broadband P and S arrivals, exploiting the density and spatial aperture of the USArray data coverage to resolve fine-scale structures. As the TA progressively moves eastward, special effort will be focused on the mid- and deep mantle beneath Central America and the Gulf of Mexico, where tomographic models indicate a tabular high velocity structure extending through the lower mantle and spreading broadly in the D" region, putatively associated with the Farallon slab and the long history of subduction beneath North America. The velocity gradients, structural continuity, structural fabric, and spatial extent of this feature will be examined using combined travel time and migration methods, with 2.5D and 3D synthetic seismogram modeling being used to quantify the elastic and anisotropic structure. Corresponding downwelling structure deep beneath the subduction zone under Alaska will be analyzed, and the two convergent zone regions will be compared to the eastern Central Pacific structure where there is an abrupt lateral transition from a chemically-distinct large low shear velocity province to adjacent higher velocity structure in the D" region. Continued collaborations with mineral physics and geodynamic colleagues will allow us to explore connections between shallow and deep structures in the mantle and their dynamic implications for tectonics and evolution of the North American continent.