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: 1315856
• 负责人: Brandon Schmandt
• 金额: $ 23.09万
• 依托单位: University of New Mexico
• 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 2017-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1315856&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.

对岩石圈结构的详细地震研究将检验两个假设，该假设是伊莎贝拉高地震速度异常在加利福尼亚州南部大山谷上地幔中的构造起源。这两个假设都是根据现有的地震成像的可行性，该地震成像使用了相距约70公里的站点的数据，但它们对伴随俯冲终止的过程和大陆弧岩石圈的演变具有截然不同的含义。一个假设将伊莎贝拉异常归因于内华达山脉南部山地球的沉没镁铁质根。其他属性将伊莎贝拉异常归因于化石板，这是蒙特雷微板的延续，在大山谷下方相干地翻译，因为它机械地与太平洋板块耦合。重要的是，后者的假设将化石平板放在圣安德烈亚斯断层段的沿着距离范围之下，该片段主要由Aseismic Creep畸形，并容纳了深层构造构成震颤，这可能是由平板上的流体引起的。使用密集的宽带阵列的被动源地震成像，从海岸到内华达山脉山脉延伸约7 km站间距，将牢固地测试两个假设，并通过岩石圈接口的详细映射进行详细的映射，并识别它们是否连续跨板界面，并在300 km的额定右手置换式置换式位置。散射的波浪迁移和断层成像方法将在协调一致地限制密集阵列下的岩石圈结构。地震研究将进一步了解俯冲终止的结构遗产和力学，内华达山脉岩石岩岩石圈的分散后进化以及当今圣安德烈亚斯断层蠕变部分的基础边界条件。不仅可以通过对基本构造过程的潜在影响来确定一个明显的科学进步机会，而且还存在两个岩石圈尺度结构的两个明确定义的假设，这些假设可以通过现代的被动源地震成像方法进行了重视。该项目的其他影响包括帮助开发新墨西哥大学（UNM）新的地球物理小组，通过支持初学者PI，研究生和本科研究人员的发展。在新墨西哥州，最大的机构扩大地球物理研究和教学的扩大具有吸引代表性不足的少数民族的杰出潜力。加州理工学院将为研究生和本科研究人员提供支持。该项目将在UNM和CalTech之间建立新的合作。

项目成果

P and S Wave Receiver Function Imaging of Subduction With Scattering Kernels: RECEIVER FUNCTION KERNEL IMAGING

使用散射核对俯冲带进行 P 和 S 波接收函数成像：接收函数核成像

• DOI: 10.1002/2017gc007120
• 发表时间: 2017
• 期刊: Geosystems
• 作者: Hansen, S. M.;Schmandt, B.
• 通讯作者: Schmandt, B.

Rayleigh and S wave tomography constraints on subduction termination and lithospheric foundering in central California

瑞利和 S 波层析成像对加利福尼亚州中部俯冲终止和岩石圈沉没的限制

• DOI: 10.1016/j.epsl.2018.02.009
• 发表时间: 2018
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Jiang, Chengxin;Schmandt, Brandon;Hansen, Steven M.;Dougherty, Sara L.;Clayton, Robert W.;Farrell, Jamie;Lin, Fan-Chi
• 通讯作者: Lin, Fan-Chi