Adjoint tomography of the crustal and upper-mantle seismic structure beneath Continental China

东亚地区以其独特的印度-亚洲大陆碰撞、不同类型的板块俯冲、多种类型的含油气盆地形成、广泛的陆内裂谷作用、板内火山作用和岩浆作用等复杂的构造活动而备受地球科学家的关注。追踪这些构造活动背后的驱动力是至关重要的，以了解如何古老的大陆根，大陆和海洋板块在板块边缘，地幔流动的岩石圈相互作用在一个动态的地球框架。是吗？获取高清晰度多参数地球地震图像的关键是什么？的内部，以测试不同的假设的构造驱动力，如地壳缩短或/和印度板块俯冲造成的隆起？全世界屋顶？青藏高原、下地幔柱或/和地幔过渡带（410？650 km深处），导致热地幔上涌，形成中朝边界沿着的长白山板内火山;太平洋板块俯冲和后滚，导致中国东部岩石圈拉张、平移和减薄，以及日本和华南边缘海的张开。在这项研究中，地震成像将映射地震记录的全波形，以呈现更逼真的模型，代表地球？的内部属性。这一成果不仅将为构造形成机制的端元检验提供独立而强有力的地震学约束，而且将为岩石圈和上地幔的成分、热状态、流动和组构结构提供新的认识，与地质学、地球化学、岩石学、中国及其周边地区的密集阵列台站记录的前所未有的地震波形数据集将用于地壳成像和上地幔结构。该数据集由CEArray、NECESS Array、INDEPTH-IV Array、F-net和其他全球和区域地震网络的地震记录组成。与传统的基于射线理论的地震成像相反，本研究的伴随层析成像考虑了全三维波传播效应和射线路径敏感性。在该实现中，它利用谱元法进行精确的波传播模拟。层析成像方法从3D初始模型开始，该模型将平滑的径向各向异性地幔模型S362 ANI与3D地壳模型Crust2.0相结合（可能最近发布的Crust1.0可用于更准确和更高分辨率的模型细化）。基于共轭梯度法，利用为每个更新的3D模型计算的3D有限频率内核，迭代地最小化走时和振幅失配。大规模并行模拟是在XSEDE超级计算机上进行的，通过现有的XSEDE研究分配给团队。最终的模型将允许仔细检查东亚不同构造单元下的地震结构，并更好地了解地下过程如何塑造地表地质和构造特征。初步结果已经表明，地壳和上地幔的非均匀性与喜马拉雅地块、青藏高原、塔里木盆地、鄂尔多斯地块和四川盆地等地表构造单元之间有很强的相关性。在过渡区上方的平滑初始模型中出现了窄板特征。初步模型中的3D波速变化与先前研究中的高频P波和S波断层图像相当或更尖锐。将进行额外的迭代，以完善三维径向各向异性模型，并解决三维方位各向异性和衰减，这是密切相关的地幔流变学和地壳和岩石圈应变速率和流动。该提案将支持一名研究生和一名研究科学家。这项研究的结果也将有更广泛的影响，了解三维波速不均匀性和孕震过程之间的联系。更现实的高清晰度模型将有助于评估地震危险性，提供更准确的地面运动图，更可靠的滑动预测和未来灾难性地震的有限断层表面上的破裂估计。最后的模型将被存档和分发，用于地质学、地球化学、岩石学、地球动力学和火山学等地球科学其他领域的定量研究。利用Rice现有的3D可视化实验室设施，地球模型可以随时向公众展示，以促进地球科学。最后，研究结果将加强中美之间的科学交流，扩大未来的潜在合作。

East Asia has drawn much attention of geoscientists due to its complicated zoo of tectonic activities: unique continent-continent collision of India and Asia, different styles of plate subduction, various types of hydrocarbon-bearing basin formation, widespread intracontinental rifting, intraplate volcanism and magamatism. Tracing the driving forces behind these tectonic activities is vital to understand how the ancient continental roots, continental and oceanic plates at the plate margins, and mantle flows underlying lithosphere interact amongst each other in a dynamic earth framework. It?s essential to obtain high-definition multi-parameter seismic images of the earth?s interior to test different hypotheses of the tectonic driving forces, such as crustal shortening or/and Indian plate underthrusting causing the uplift of ?the world?s roof?, the Tibetan Plateau, lower-mantle plume or/and dehydration from the stagnant slab in the mantle transition zone (410 ? 650 km depths) inducing hot mantle upwelling contributing to the intraplate volcano Changbaishan along the border of China and North Korea, and the Pacific slab subduction and rollback producing extension, transtension, and thinning of the lithosphere beneath the East China and opening of the marginal seas of Japan and South China. Seismic imaging in this study will map full waveforms of seismic records to render more realistic models representing the earth?s interior properties. The outcome will not only provide the independent and robust seismological constrains to test the end members of tectonic formation mechanism, but also shed new light on the composition, thermal state, flow and fabric structure of the lithosphere and upper mantle, which are complementary to geological, geochemical, petrological, and geodetic observations of East Asia.An unprecedented seismic waveform dataset recorded by very dense array stations in China and its surrounding regions will be used to image the crust and upper-mantle structure beneath the East Asia. This dataset is comprised of seismic records from the CEArray, the NECESSArray, the INDEPTH-IV Array, F-net and other global and regional seismic networks. Contrary to traditional ray-theory based seismic imaging, adjoint tomography of this study takes into account full 3D wave propagation effects and off-ray-path sensitivity. In this implementation, it utilizes a spectral-element method for precise wave propagation simulations. The tomographic method starts with a 3D initial model that combines the smooth radially anisotropic mantle model S362ANI with 3D crustal model Crust2.0 (potentially recently released Crust1.0 can be used for more accurate and higher resolution model refinement). Traveltime and amplitude misfits are minimized iteratively based on a conjugate gradient method, harnessing 3D finite-frequency kernels computed for each updated 3D model. The massively parallel simulations are carried out on XSEDE supercomputers available to the team via an existing XSEDE research allocation. The final models will allow close examination of seismic structures beneath different tectonic units of East Asia, and better understanding of how sub-surface processes shaping surface geology and tectonic features. The preliminary results already show strong correlations between heterogeneities in the crust and upper mantle with surface tectonic units, such as the Himalaya Block, the Tibetan Plateau, the Tarim Basin, the Ordos Block, and the Sichuan Basin. Narrow slab features emerge from the smooth initial model above the transition zone. 3D wavespeed variations in the preliminary model are either comparable to or sharper than high-frequency P- and S-wave tomographic images from previous studies. Additional iterations will be carried out to refine the 3D radially anisotropic models, and to resolve 3D azimuthal anisotropy and attenuation, which are closely related to mantle rheology and crustal and lithospheric strain rates and flow. This proposal will support one graduate student and one research scientist. The outcome of this research will also have a broader impact on understanding the linkage between 3D wavespeed heterogeneities and seismogenic processes. The more realistic high-definition models will help assess seismic hazard by providing more accurate ground motion maps, more robust slip predictions and rupture estimations on finite fault surfaces for future catastrophic earthquakes. The final models will be archived and distributed for quantitative studies in other fields of geoscience, such as geology, geochemistry, petrology, geodynamics and volcanology. With the existing 3D visualization lab facility at Rice, the earth models can be readily displayed to the public to promote earth science. Finally the results will enhance scientific communication between US and China and broaden future potential collaborations.