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

0453944 Garnero该项目利用USAray可移动阵列（TA）和主干阵列数据进行深部地幔结构的高分辨率地震波成像。该研究计划的目的是自然规模与TA站在美国西部的逐步部署，建立在使用加州区域网络数据获得的初步结果。我们正在分析穿越三个分区的地幔深处的地震波：美国南部-墨西哥湾-中美洲-加勒比海，在中太平洋之下，在阿拉斯加和北美北方之下。目前正在采用利用TA数据提供的相对密集的70公里测站间距的地震方法。双阵列波形叠加、3D层析模型中的基尔霍夫散射偏移、考虑方位角各向异性的剪切波分裂分析以及有限频率层析到达时间反演程序是应用于宽带P和S波形的主要方法。当最初的TA部署完成后，它将使深地幔空间采样增加5倍，相对于最近开发的局部高分辨率模型，在科科斯板块和区域框架结构，我们已经开发。特别的努力集中在中美洲和墨西哥湾下的中地幔和深地幔，在层析成像模型中有证据表明，在D”区，板状高速结构延伸穿过下地幔并广泛扩散，可能与Farallon板片和北美下的长期俯冲历史有关。正在使用到达时间分析和迁移方法检查速度梯度、结构连续性、结构组构和深部地幔结构的空间范围，并使用二维和三维合成建模来量化结构和验证成像程序的可靠性。分析了阿拉斯加俯冲带下的相应构造，并将这两个会聚带区域与中太平洋下的孤立构造进行了比较。我们正在评估板状物质、后钙钛矿相变、深部地幔动态流动和部分熔融对深部地幔结构的贡献。这些分析将与Earthscope对浅地幔结构的调查密切协调，并根据其他人发现的接收器结构、岩石圈各向异性和上地幔旅行时间变化的模型进行校正。我们的目标是利用USAray数据，在理解深部地幔结构及其与北美大陆向西移相关的中上地幔流的关系方面取得突破性进展。

0453944GarneroThis project utilizes USArray Transportable Array (TA) and Backbone Array data in high-resolution seismic wave imaging of deep mantle structure. The research plan is designed to scale naturally with the progressive deployment of TA stations in the western U.S, building upon initial results obtained using California regional network data. We are analyzing teleseismic earthquake waves that traverse the deep mantle in three subregions: beneath the southern U.S.-Gulf of Mexico-Central America-Caribbean, under the Central Pacific, and beneath Alaska and northern North America. Seismic methodologies that exploit the relatively dense 70-km station spacing provided by the TA data are being applied. Double-array waveform stacking, Kirchhoff scattering migration in 3D tomographic models, shear-wave splitting analysis allowing for azimuthal anisotropy, and finite frequency tomographic arrival time inversion procedures are the primary methods being applied to broadband P and S waveforms. When the initial TA deployment is completed, it will enable 5-fold increase in deep mantle spatial sampling relative to recently developed localized high resolution models for beneath the Cocos Plate and regional framework structures that we have developed. Particular effort is being focused on the mid- and deep mantle beneath Central America and the Gulf of Mexico, where there is evidence in tomographic models for tabular high velocity structures extending through the lower mantle and spreading broadly in the D" Region, possibly associated with the Farallon slab and with the long history of subduction beneath North America. The velocity gradients, structural continuity, structural fabric, and spatial extent of the deep mantle structure is being examined using arrival time analysis and migration methods, with 2D and 3D synthetic modeling being used to quantify structures and to verify the reliability of the imaging procedures. Corresponding structure beneath the subduction zone under Alaska is being analyzed, and these two convergent zone regions are being compared to the isolated structure under the Central Pacific. We are assessing contributions to deep mantle structure from slab material, a post-perovskite phase transition, deep mantle dynamic flow, and partial melting. These analyses will be closely coordinated with Earthscope investigations of shallow mantle structure, incorporating corrections based on models found by others for receiver structure, lithospheric anisotropy, and upper mantle travel time variations. Our goal is to exploit USArray data to make breakthrough advances in understanding of deep mantle structure and its relationship to mid- and upper-mantle flow associated with the westward movement of the North American continent.