Variations Along a Continental Convergent Margin: Seismic imaging of the western margin of South America

会聚边缘，即大洋板块潜入大陆板块边缘之下的地方，是包括世界在内的许多地球基本过程和特征的所在地吗？S最大的地震，最长的火山链和一些最年轻的超级火山喷发，还有世界上最长的山脉之一？S最长的山脉，安第斯山脉。南美洲西缘之下的太平洋板块俯冲构成了地球上最大的洋-陆会聚边缘系统，因此是研究这些重要过程和特征的理想场所。我们建议利用横跨安第斯山脉中部4000多公里的1000多个永久和便携式地震台站的现有地震数据来研究南美会聚边缘的一大部分。我们将使用现代计算技术来生成安第斯山脉下深达1000公里的地下地震图像。通过使用这些新的地震图像，我们的具体科学目标是提高我们对地震和火山如何建造和摧毁山脉，以及水是否以及如何被输送到地球深处的理解。这个项目将在亚利桑那大学地震学小组和我们在秘鲁、玻利维亚、智利、阿根廷和巴西的科学合作者20年来在该地区所做工作的基础上进行和综合。更广泛的影响包括对研究生进行现代地震技术培训，以及加强我们在南美的国际合作。地震方法有可能提供从上地壳到下地幔的最高分辨率的地球图像。我们将使用面波层析成像、有限频率远震走时层析成像(P&P；S波和波速比)、接收函数以及面波数据和接收函数的联合反演来产生南美洲西部边缘的统一地震图像。使用我们新开发的地震图像，我们的具体科学目标是：？评估分层在安第斯山脉建造中的顺向作用。研究地壳缩短的下地壳可容空间沿走向的变化，包括纯剪切增厚、低地壳流动和高角度莫霍面切割断层。重新讨论岩浆添加在安第斯地壳增厚中的重要性的问题。？研究俯冲的纳斯卡板块穿透地幔过渡带时的变形，以及深俯冲流体在地幔过渡带和板块下方的作用。该项目将通过产生一套统一的南美洲西缘大型沿走向地区的高分辨率地震图像，增加我们对造山、地壳变形和俯冲过程的认识。有了统一的地震图像，我们可以更好地评估产生高海拔的不同机制和沿走向变化的原因。我们的最后一个目标是提高我们对纳斯卡板和周围地幔更深层次结构的理解。我们改进的地震图像将帮助我们评估地幔过渡带中水的存在和路径。

Convergent margins, where an oceanic plate dives under the edge of a continental plate, are the sites of many fundamental Earth processes and features that include the world?s largest earthquakes, the longest volcanic chains with some of the youngest supervolcano eruptions, and one of the world?s longest mountain ranges, the Andes. The subduction of the (Pacific) oceanic plate beneath the western margin of South America constitutes the largest ocean-continent convergent margin system on Earth, and hence, is an ideal location to study these important processes and features. We propose to study a large portion of the South American convergent margin by taking advantage of existing seismic data from over 1000 permanent and portable seismic stations that span over 4000 km of the central Andes. We will use modern computational techniques to generate seismic images of the subsurface beneath the Andes to depths as great as 1000 km. By using these new seismic images, our specific scientific goals are to improve our understanding of how earthquakes and volcanoes are building and destroying the mountains, and whether and how water is transported to great depths in the Earth. This project will build on and synthesize two decades of work in the region by the seismology group at the University of Arizona and our scientific collaborators in Peru, Bolivia, Chile, Argentina, and Brazil. The broader impacts include training graduate students in modern seismic techniques and strengthening our international collaborations in South America. Seismic methods potentially provide the highest resolution images of the Earth from the upper crust to the lower mantle. We will use Surface Wave Tomography, Finite-Frequency Teleseismic Travel Time Tomography (P- & S-wave and Vp/Vs), Receiver Functions and a joint inversion of Surface Wave Data and Receiver Functions to produce uniform seismic images of the western margin of South America. Using our newly developed seismic images, our specific scientific goals are to:? Evaluate the along strike role of delamination in the building of the Andes.? Investigate the along strike variability in lower crustal accommodation of crustal shortening, including pure shear thickening, lower crustal flow, and high-angle Moho-cutting faults.? Revisit the question of the importance of magmatic addition in the thickening of the Andean crust. ? Investigate the deformation of the subducted Nazca slab as it penetrates the mantle transition zone, and the role of deeply subducted fluids in the mantle transition zone and below the slab.This project will increase our knowledge about mountain building, crustal deformation and the subduction process by producing a uniform set of high-resolution seismic images of a large along-strike region of the western margin of South America. With uniform seismic images, we can better evaluate different mechanisms that create high elevations and the causes of along-strike variability. Our last goal is related to improving our understanding of the deeper structure of the Nazca slab and the surrounding mantle. Our improved seismic images will help us evaluate the presence of and pathways for water in the mantle transition zone.