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

USArrow可移动阵列(TA)和主干阵列数据将用于对深部地幔结构和过程的高分辨率地震分析，其基础是使用EarthScope部署的最初5年的数据所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合作，分析横跨三个分区域的地幔深处的远程地震信号：美国南部墨西哥湾-中美洲-加勒比海之下，东太平洋和中太平洋下面，以及阿拉斯加和北太平洋下面。波形叠加、Born散射偏移、横波分裂和2.5D/3D波形模拟程序将应用于宽带P和S到达，利用US阵列数据覆盖的密度和空间孔径来解析精细结构。随着TA逐渐向东移动，特别的努力将集中在中美洲和墨西哥湾下面的中深地幔上，那里的层析模型表明，一个板状的高速结构延伸穿过下地幔，并在D“地区广泛分布，推测与Farallon板块和北美下方漫长的俯冲历史有关。这一特征的速度梯度、结构连续性、结构组构和空间范围将使用旅行时和偏移相结合的方法进行检查，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。将分析阿拉斯加俯冲带深处对应的下沉构造，并将这两个会聚带区与中东太平洋构造进行比较，中东太平洋构造在D“区从化学上截然不同的大的低剪切速度区向邻近的高速度结构突然横向转变。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浅部和深部结构之间的联系及其对北美大陆构造和演化的动力学影响。

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.