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

会聚边缘，即海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基本地球过程和特征的发生地。最大的地震，最长的火山链和一些最年轻的超级火山爆发，以及世界上最大的地震之一？世界上最长的山脉是安第斯山脉。 南美洲西缘之下的（太平洋）大洋板块的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地点。我们建议利用现有的地震数据，从1000多个永久性和便携式地震台站，跨越4000公里的中部安第斯山脉的大部分南美会聚边缘的研究。 我们将利用现代计算技术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的理解，以及水是否以及如何被输送到地球深处。该项目将以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在该地区20年的工作为基础，并将其综合。更广泛的影响包括培训研究生现代地震技术和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、双频遥测地震走时层析成像（P-S波和Vp/Vs）、接收器函数以及面波数据和接收器函数的联合反演来产生南美洲西缘的统一地震图像。 利用我们新开发的地震图像，我们的具体科学目标是：？评价分层在安第斯山脉建造中的沿着走向作用。调查地壳缩短的下地壳可容纳性的沿着走向变化，包括纯剪切增厚、下地壳流动和高角度莫霍面切割断层。重新讨论岩浆增加在安第斯地壳增厚中的重要性问题。?调查俯冲的纳斯卡板块在穿透地幔过渡带时的变形情况，以及地幔过渡带和板块之下深度俯冲流体的作用，该项目将通过制作南美洲西缘一个大的走向地区的一套统一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了解。 通过统一的地震图像，我们可以更好地评估造成高海拔的不同机制以及沿走向变化的原因。 我们的最后一个目标是提高我们对纳斯卡板块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.