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

沿大陆辐合边缘的变化：南美洲西缘的地震成像

• 批准号: 1415914
• 负责人: Susan Beck
• 金额: $ 37.5万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-10-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1415914&HistoricalAwards=false
• 关键词: Variations; Along; Continental; Convergent; Margin

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.

融合边缘，海洋板在大陆板的边缘下面潜水，是许多基本的地球过程和特征的地点，包括世界上最大的地震，最长的火山链，以及一些最年轻的Supervolcano pruptions，以及世界上最长的山区山脉。 南美西部边缘下方（太平洋）海洋板的俯冲构成地球上最大的海洋融合边缘系统，因此是研究这些重要过程和特征的理想场所。我们建议通过利用1000多个永久和便携式地震站的现有地震数据来研究南美融合边缘的大部分，这些数据占安第斯山脉中部4000公里以上。 我们将使用现代的计算技术来生成安第斯山脉下面的地下的地震图像，深度高达1000公里。 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破坏山脉的理解，以及是否以及如何将水运到地球深处。该项目将由亚利桑那大学的地震学小组以及我们在秘鲁，玻利维亚，智利，阿根廷和巴西的科学合作者在该地区的二十年工作。更广泛的影响包括现代地震技术的培训研究生以及加强我们在南美的国际合作。 地震方法可能会提供从地壳到下地幔的地球最高分辨率图像。我们将使用表面波断层扫描，有限频率的远距离旅行时间断层扫描（P＆S-WAVE和VP/VP），接收器功能以及表面波数据和接收器功能的联合反转，以产生南美西部边缘的均匀地震图像。 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的建设中的及时罢工作用。研究地壳缩短的下层地壳适应性的沿袭变异性，包括纯剪切增厚，较低的地壳流量和高角度的Moho切割断层。重新审视岩浆添加在安第斯外壳增厚中的重要性的问题。 ？ 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. 借助统一的地震图像，我们可以更好地评估产生高海拔的不同机制和造成撞击变异性的原因。 我们的最后一个目标与提高我们对纳斯卡板和周围地幔更深层次结构的理解有关。我们改进的地震图像将有助于我们评估地幔过渡区中水的存在和途径。

项目成果

Segmentation in continental forearcs: Links between large-scale overriding plate structure and seismogenic behavior associated with the 2010 M 8.8 Maule, Chile earthquake

• DOI: 10.1016/j.tecto.2019.228164
• 发表时间: 2019-09
• 期刊: Tectonophysics
• 影响因子: 2.9
• 作者: Brandon T. Bishop;S. Beck;G. Zandt