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.

汇聚边缘，即海洋板块潜入大陆板块边缘的地方，是许多基本地球过程和特征的所在地，包括世界上最大的地震、最长的火山链和一些最年轻的超级火山喷发，以及世界上最长的山脉之一安第斯山脉。 南美洲西缘下方的（太平洋）海洋板块俯冲构成了地球上最大的洋-陆汇聚边缘系统，因此是研究这些重要过程和特征的理想地点。我们建议利用跨越安第斯山脉中部 4000 多公里的 1000 多个永久和便携式地震台的现有地震数据来研究南美会聚边缘的大部分地区。 我们将使用现代计算技术生成安第斯山脉地下 1000 公里深处的地震图像。 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输送到地球深处的理解。该项目将建立并综合亚利桑那大学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二十年的工作。更广泛的影响包括培训研究生现代地震技术以及加强我们在南美的国际合作。 地震方法有可能提供地球从上地壳到下地幔的最高分辨率图像。我们将使用面波层析成像、有限频率远震走时层析成像（P 波和 S 波以及 Vp/Vs）、接收函数以及面波数据和接收函数的联合反演来生成南美洲西缘的均匀地震图像。 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建设中的沿袭作用。研究地壳缩短的下地壳调节的沿走向变化，包括纯剪切增厚、下地壳流动和高角度莫霍面切割断层。重新审视岩浆添加对安第斯地壳增厚的重要性问题。 ？研究俯冲纳斯卡板块在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。该项目将通过生成南美洲西缘大型沿走向区域的一组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。 借助统一的地震图像，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片和周围地幔深层结构的理解。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。

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