Collaborative Research: Investigating Temperature, Melting, and Mantle Flow in the North American Upper Mantle with 3-D Models of Shear Velocity, Radial Anisotropy, and Attenuation

合作研究：利用剪切速度、径向各向异性和衰减的 3D 模型研究北美上地幔的温度、熔化和地幔流动

• 批准号: 1252039
• 负责人: James Gaherty
• 金额: $ 10.29万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-15 至 2016-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1252039&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Temperature; Melting

The continent of North America is geologically and tectonically diverse. The western half of the continent includes a major plate boundary and has been host to mountain-building events, volcanism, and extension within the recent geological past. The eastern portion of North America is located far from any plate boundary and has not experienced significant tectonic activity in hundreds of millions of years. Understanding how the dynamic processes occurring in Earth's interior have given rise to this complex terrain is fundamental to understanding the growth and evolution of continents in general and North America in particular. Imaging variations in the speed of seismic waves traveling through the crust and mantle provides important constraints on the temperature and composition of those regions as well as the presence of partially molten rock. However, since each of these factors, and any combination of them, can affect velocity, additional data sets are needed to achieve a robust interpretation. The absorption of seismic-wave energy is also controlled by temperature, composition, and melt content, and thus jointly interpreting variations in seismic-wave velocity and attenuation allows for improved constraints on the properties of Earth's interior. To date, there have been very few studies of seismic attenuation beneath North America, largely because of the difficulties involved with measuring and analyzing the amplitudes of seismic waves. The PIs will develop 3-D models of shear attenuation and radially anisotropic shear velocity for the North American upper mantle using surface waves recorded by USArray. Surface-wave phase and amplitude are measured using a new interstation cross-correlation approach that exploits waveform similarity at nearby stations, and the phase and amplitude data will be utilized together to take advantage of the dependence of both data sets on seismic velocity and attenuation. From these models, variations in temperature, composition, and partial melt across the continent will be estimated, and a more complete picture of how structures like the Colorado Plateau, the Basin and Range, the Mid-Continent Rift, and the North American craton are controlled by the processes in and properties of the underlying mantle will emerge.

北美大陆在地质和构造上是多样的。该大陆的西半部分包括一个主要的板块边界，并在最近的地质过去一直举办山区建设事件，火山和延伸。北美的东部远离任何板块边界，在数亿年内没有经历过重大的构造活动。了解地球内部的动态过程是如何引起这一复杂地形的方式，这对于了解一般和北美大陆的生长和演变至关重要。穿过地壳和地幔的地震波速度的成像变化为这些区域的温度和组成以及部分熔融岩石的存在提供了重要的限制。但是，由于这些因素中的每一个以及它们的任何组合都可能影响速度，因此需要其他数据集来实现强大的解释。 地震波能量的吸收也受温度，成分和熔体含量的控制，从而共同解释地震波速度的变化和衰减可以改善对地球内部特性的约束。迄今为止，很少有关于北美下的地震衰减的研究，这主要是因为在测量和分析地震波的幅度上涉及的困难。 PI将使用USArray记录的表面波开发3-D模型的剪切衰减和径向各向异性剪切速度。使用新的间互相关方法来测量地表波相和振幅，该方法利用了附近站点的波形相似性，并且将共同利用相位和振幅数据来利用这两个数据集对地震速度和衰减的依赖性。从这些模型中，将估算整个大陆的温度，成分和部分熔体的变化，并更完整地了解科罗拉多高原，盆地和范围，中间裂谷和北美克拉顿等结构如何受底层地下室的过程和特性的控制。