Seismological studies of cratonic lithosphere: investigating lithospheric rheology, heat flow beneath ice sheets, and the origin of mid-lithospheric discontinuities

克拉通岩石圈的地震学研究：研究岩石圈流变学、冰盖下的热流以及岩石圈中部不连续面的起源

• 批准号: 2044136
• 负责人: Colleen Dalton
• 金额: $ 43.76万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2044136&HistoricalAwards=false
• 关键词: Seismological; studies; cratonic; lithosphere; investigating

There are fundamental differences between the oceanic crust that comprises the seafloor and the continental crust on which humans live. Continental crust is thicker and lighter than oceanic crust. It is also, on average, much older: the oldest oceanic crust is 200 million years whereas the oldest continental crust is 4300 million years. All of these differences—thickness, buoyancy, and age—can be attributed to the properties of and the processes occurring within the Earth’s mantle. This study will use seismic waves generated by earthquakes to image the mantle beneath continents, employing methods similar to those used to perform CT scans on the human body. The study will seek to answer questions about how the events that formed and subsequently modified the continents imbued them with their buoyancy and longevity, which are crucial to their habitability. In terms of broader impacts, the project will support one graduate student and several undergraduates, including at least one from an under-represented group in STEM. This study will advance understanding of the processes that form and modify cratons by developing new models of the seismic attenuation, velocity, and anisotropy structure at several cratons around the globe. To accomplish this, the study will: (1) perform co-located analyses of Rayleigh wave attenuation and anisotropic phase velocity, Ps and Sp receiver functions, and shear-wave splitting; (2) determine depth-dependent models of shear velocity, shear attenuation, and azimuthal anisotropy from the body- and surface-wave data using both forward and inverse approaches; (3) test hypotheses for the origin of midlithospheric discontinuities by interpreting the seismic models together with the elastic properties of peridotite and hydrous phases and with anelasticity experiments; (4) through incorporation of mantle-xenolith and heat-flow data, develop a method for estimating lithospheric thermal and chemical structure that can be applied in ice-covered regions.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.

包括海底的海洋壳和人类居住的连续地壳之间存在根本差异。大陆地壳比海洋壳厚，更轻。平均而言，它的年龄也很大：最古老的海壳是2亿年，而最古老的连续地壳是4.3亿年。所有这些差异（厚度，浮力和年龄）都归因于地球内地幔中的特性和过程。这项研究将使用地震产生的地震波来对下面的地幔进行成像，采用类似于用于对人体进行CT扫描的方法。该研究将寻求回答有关形成和随后改变大陆的事件如何使它们充满浮力和寿命的问题，这对于它们的居住性至关重要。在更广泛的影响方面，该项目将支持一名研究生和几名本科生，其中包括来自STEM中代表性不足的群体的至少一个。这项研究将通过开发全球多个craton的地震衰减，速度和各向异性结构的新模型来提高对形成和修改克拉通的过程的理解。为此，研究将：（1）对瑞利波衰减和各向异性相速度，PS和SP接收器功能以及剪切波分裂进行共同确定的分析； （2）使用前进和反向方法确定剪切速度，剪切衰减和方位角各向异性的深度依赖模型； （3）通过解释地震模型以及橄榄岩和氢相的弹性特性以及不弹性实验来解释地震模型，以测试中段圈不连续性的起源。 （4）通过掺入地幔 - Xenolith和热流数据，开发了一种估算岩石圈热和化学结构的方法，可以在冰覆盖的区域中应用，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影响的审查审查标准来通过评估来通过评估来支持的。