Collaborative Research: Is the Isabella anomaly a fossil slab or the foundered lithospheric root of the Sierra Nevada batholith?

合作研究：伊莎贝拉异常是一块化石板还是内华达山脉基岩沉没的岩石圈根部？

• 批准号: 1314910
• 负责人: Robert Clayton
• 金额: $ 13.65万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-15 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1314910&HistoricalAwards=false
• 关键词: Collaborative; Research; Isabella; anomaly; fossil

A detailed seismic investigation of lithospheric structure will test two hypotheses for the tectonic origin of the Isabella high seismic velocity anomaly in the upper mantle of California's southern Great Valley. Both hypotheses are viable based on existing seismic imaging that uses data from stations spaced about 70 km apart, but they have dramatically different implications for the processes that accompany subduction termination and the evolution of continental arc lithosphere. One hypothesis attributes the Isabella Anomaly to the sinking mafic root of the southern Sierra Nevada batholith. The other attributes the Isabella Anomaly to a fossil slab that is a continuation of the Monterey microplate coherently translating beneath the Great Valley because it is mechanically coupled to the Pacific plate. Importantly, the latter hypothesis places the fossil slab beneath the along-strike extent of the section of the San Andreas fault that dominantly deforms by aseismic creep and hosts deep crustal tectonic tremor, which might be caused by fluids from the slab. Passive source seismic imaging using a dense broadband array with ~7 km station spacing extending from the coast to the Sierra Nevada foothills will robustly test the two hypotheses with detailed mapping of lithospheric interfaces and identification of whether or not they are continuous across a plate bounding fault with 300 km of cumulative right lateral displacement. Scattered wave migration and tomographic imaging methods will be used in concert to constrain lithospheric structure beneath the dense array. The seismic study will advance understanding of the structural legacy and mechanics of subduction termination, post-subduction evolution of the Sierra Nevada arc lithosphere, and present day basal boundary conditions on the creeping section of the San Andreas fault. A clear opportunity for scientific advance is identified not only by the potential implications for fundamental tectonic processes, but also by the existence of two well-defined hypotheses for lithospheric-scale structure that can be robustly tested with modern passive source seismic imaging methods. Additional impacts of the project include aiding in the development of a new geophysics group at the University of New Mexico (UNM) by supporting a beginning-career PI, a graduate student, and an undergraduate researcher. Expansion of geophysics research and teaching at the state of New Mexico?s largest institution has outstanding potential to attract under-represented minorities to opportunities in the geosciences. A graduate student and undergraduate researcher will be supported at Caltech. The project will develop a new collaboration between UNM and Caltech.

对岩石圈结构进行详细的地震调查将检验加州南部大峡谷上地幔伊莎贝拉高地震速度异常的构造起源的两种假设。这两种假设都是可行的基础上，现有的地震成像，使用的数据站间隔约70公里，但他们有显着不同的影响，伴随着俯冲终止和大陆弧岩石圈的演化过程。有一种假说认为伊莎贝拉异常是由于内华达州南部山脉的基性岩根下沉造成的。另一种将伊莎贝拉异常归因于化石板，它是蒙特雷微板块的延续，因为它与太平洋板块机械耦合，所以在大峡谷下面连贯地平移。重要的是，后一种假设将化石板置于圣安德烈亚斯断层部分的沿走向范围之下，该断层主要由地壳蠕变变形并承载深部地壳构造震颤，这可能是由板中的流体引起的。被动源地震成像使用密集宽带阵列，从海岸延伸到内华达州山麓，站间距约为7 km，通过详细绘制岩石圈界面图和识别它们是否连续穿过累积右侧位移为300 km的板块边界断层，将有力地检验这两个假设。散射波偏移和层析成像的方法将被用于协调一致，以约束岩石圈结构下的密集阵列。地震研究将促进对俯冲终止的结构遗产和力学、内华达州山脉岛弧岩石圈的俯冲后演化以及圣安德烈亚斯断层蠕动段现今基底边界条件的理解。一个明确的机会，科学进步的确定，不仅是潜在的影响，基本的构造过程，而且存在两个定义明确的假设，岩石圈尺度的结构，可以与现代被动源地震成像方法进行有力的测试。该项目的其他影响包括通过支持一名职业PI、一名研究生和一名本科生研究员，帮助新墨西哥州大学（UNM）发展一个新的物理学小组。在新墨西哥州扩大物理学研究和教学？美国最大的机构具有吸引代表性不足的少数民族在地球科学的机会突出的潜力。加州理工学院将支持一名研究生和一名本科生研究员。该项目将开发UNM和加州理工学院之间的新合作。