Characterization of the Oceanic Lithosphere-Asthenosphere Boundary in the Colombian Subduction Zone through Receiver Function Analysis

通过接收函数分析表征哥伦比亚俯冲带海洋岩石圈-软流圈边界

• 批准号: 2041631
• 负责人: Brandon Bishop
• 金额: $ 24.36万
• 依托单位: Saint Louis University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2041631&HistoricalAwards=false
• 关键词: Characterization; Oceanic; Lithosphere; Asthenosphere; Boundary

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).The goal of this project is to test two competing models of the boundary separating the Earth’s stiff outer layer (lithosphere) from the underlying, weaker layer (asthenosphere). One model proposes that this boundary is a narrow channel that decouples the lithosphere and asthenosphere. The other model proposes that this boundary forms a broad band of deformation that couples the lithosphere and asthenosphere. Each model has important implications for our understanding of plate tectonics—the process which drives the Earth’s long-term geologic evolution—and its relation to the Earth’s interior. Each model carries predictions about the boundary between the lithosphere and asthenosphere. These predictions can be tested using receiver functions. In collaboration with the Universidad Nacional de Colombia, this project uses recordings from seismic stations of the Colombian National Seismic Network located above the Colombian subduction zone. In this region, the characteristics of Nazca oceanic plate’s lower boundary can be examined over a range of depths to determine which of the models is most accurate. Understanding which model is most accurate will benefit society by helping to constrain the force balance acting on tectonic plates, especially around subduction zones where potentially destructive earthquakes driven by these forces occur. This project further benefits society by deepening international collaboration between institutions in the US and Colombia as well as furthering STEM education by providing training in seismology to a postdoctoral fellow.Observations of the oceanic lithosphere-asthenosphere boundary (LAB) support two categories of contradictory models for coupling between the lithosphere and underlying asthenosphere, and correspondingly contradictory implications for plate tectonics. One category interprets the boundary to be a narrow, melt-rich channel that decouples lithospheric plates from the asthenosphere. Plate motion is thus driven largely by slab pull. The other category interprets the boundary as a broad zone which couples plates to the asthenosphere. Plate motion is thus strongly influenced by asthenospheric flow induced drag. These models predict differing structures and localizations of shear along the LAB. Channel models predict two closely spaced, highly sheared boundaries while coupled models predict either a single boundary with little shear or a single highly sheared boundary. The predicted features respond differently to increasing pressure due to subduction. Channels narrow with depth and coupled structures persist to greater, differing depths, so observing a plate as it subducts offers an ideal natural experiment to test these models. Seismic waves with different frequency contents interact with these structures such that high frequencies can better image channels while low frequencies can better image coupled structures. This project uses P-to-S-wave receiver function analysis of radial and transverse components recorded at broadband seismic stations to examine structural characteristics and shear localization along the boundary. The complete characterization of structure and anisotropy caused by shear requires long-term observations at seismic stations from the coast to the back arc at a range of frequency bands. This project uses data from 2010 to the present from 26 stations in the Colombian National Seismic Network to investigate and characterize the subducting Nazca oceanic plate’s LAB from depths of 100 km at the coastline to 400 km in the back arc. These observations will provide constraints on the depth, thickness, and anisotropic properties (if present) of the boundary and use these to test the proposed models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项是根据2021年《美国救援计划法》（公法117-2）全部或部分资助的。该项目的目的是测试两个竞争模型的边界模型，将地球僵硬的外层（岩石圈）与基础较弱的较弱的层（小磷）分开。一个模型提出，该边界是一个狭窄的通道，该通道是将岩石圈和软圈分解的狭窄通道。另一个模型提出，该边界形成了一个宽阔的变形带，构成了岩石圈和软圈。每个模型都对我们对板块构造学的理解（推动地球长期地质进化的过程及其与地球内部的关系）都有重要意义。每个模型都会对岩石圈和软圈之间的边界进行预测。这些预测可以使用接收器功能进行测试。该项目与哥伦比亚大学合作，使用了位于哥伦比亚俯冲区上方的哥伦比亚国家地震网络网站的录音。在该区域中，可以在一系列深度上检查纳斯卡海洋板的下边界的特征，以确定哪种模型最准确。了解哪种模型最准确，将通过帮助限制在构造板上的力平衡来使社会受益，尤其是在俯冲带上可能破坏性地震驱动这些力量的俯冲带周围。该项目通过加深美国和哥伦比亚的机构之间的国际合作以及进一步的STEM教育，并通过向博士后研究员提供培训，从而进一步受益于社会。对海洋性岩石圈 - 心脏圈边界（LAB）的观察支持两类矛盾模型，以构成岩石圈和平台之间的矛盾模型，并相应地构成了对应于地下层层的层次。一个类别将边界解释为一个狭窄，富含熔融的通道，将岩石圈板与软圈分解。因此，板运动主要由平板拉动驱动。另一个类别将边界解释为一个宽区域，将板与小圈融合在一起。因此，小动圈流动引起的阻力对板运动受到强烈影响。这些模型预测了沿实验室剪切的区分结构和剪切的位置。通道模型预测了两个紧密间隔，高度剪切的边界，而耦合模型则可以预测一个剪切少的单个边界或一个高度剪切的边界。预测的特征对由于俯冲而增加的压力的响应有所不同。通道随着深度和耦合结构的狭窄而持续到更大，不同的深度，因此观察一个板，因为它具有托管提供理想的自然实验来测试这些模型。具有不同频率内容的地震波与这些结构相互作用，使高频可以更好地图像通道，而低频可以更好地图像耦合结构。该项目使用在宽带地震站记录的径向和横向组件的P到S波接收器功能分析，以检查沿边界的结构特征和剪切定位。剪切作用的结构和各向异性的完整表征需要在一系列频带范围内从海岸到后弧的地震站进行长期观察。该项目使用从2010年到现在的26个站点的数据在哥伦比亚国家地震网络的26个站点，以调查和表征俯冲的纳斯卡海洋板实验室的实验室，从海岸线的100公里深度到后弧400公里。这些观察结果将对边界的深度，厚度和各向异性特性（如果存在）提供限制，并使用这些特性来测试拟议的模型。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛的影响审查标准通过评估来评估的。

项目成果

A Thick, Sheared Zone at the Base of an Oceanic Plate: The Lithosphere-Asthenosphere Boundary of the Subducting Nazca Plate in Colombia as Revealed through P-to-S Receiver Functions

海洋板块底部厚厚的剪切带：通过 P-to-S 接收器函数揭示的哥伦比亚俯冲纳斯卡板块的岩石圈-软流圈边界

• 发表时间: 2022
• 期刊: AGU Fall Meeting
• 作者: Bishop, Brandon;Fernandez, Ademar;Warren, Linda M.;Pedraza, Patricia;Prieto, German A.;Dionicio, Viviana
• 通讯作者: Dionicio, Viviana

Receiver Function Derived Structural Constraints on Dynamic Processes Associated with the Young Nazca Lithosphere Subducting beneath Colombia

接收函数衍生的对与哥伦比亚下方俯冲的年轻纳斯卡岩石圈相关的动态过程的结构约束

• 发表时间: 2024
• 期刊: AGU Fall Meeting 2023
• 作者: Bishop, Brandon;Cho, Sung-Won;Warren, Linda M;Pedraza, Patricia;Prieto, German A;Dionicio, Viviana
• 通讯作者: Dionicio, Viviana