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

USAray便携式阵列（TA）和骨干阵列数据将用于深地幔结构和过程的高分辨率地震分析，建立在使用EarthScope部署最初5年的数据获得的令人兴奋的结果的基础上。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部地幔的地震信号：美国南部-墨西哥湾-中美洲-加勒比海，在太平洋东部和中部，阿拉斯加和北方太平洋下面。波形叠加、Born散射偏移、横波分裂和2.5D/3D波形建模程序将应用于宽带P波和S波到达，利用USAray数据覆盖的密度和空间孔径来解析精细尺度结构。随着TA逐渐向东移动，将特别关注中美洲和墨西哥湾下的中地幔和深部地幔，层析成像模型表明，一个板状高速结构延伸穿过下地幔，并在D”区域广泛传播，这与Farallon板片和北美下的俯冲历史有关。速度梯度，结构的连续性，结构组构，和空间范围的这一功能将使用旅行时间和迁移相结合的方法进行检查，与2.5D和3D合成地震图建模被用来量化的弹性和各向异性结构。 将分析阿拉斯加俯冲带下方深处的相应下降流结构，并将两个汇聚带区域与东中太平洋结构进行比较，在东中太平洋结构中，存在从化学性质不同的大型低剪切速度区到D”区域中相邻的较高速度结构的突然横向过渡。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及其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.