CSEDI: Testing Resolution of Deep Earth Seismic Structure Under the Pacific Using Geodynamic Models

CSEDI：利用地球动力学模型测试太平洋下地球深部地震结构的分辨率

• 批准号: 0968965
• 负责人: Ying Zhou
• 金额: $ 29万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-15 至 2015-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0968965&HistoricalAwards=false
• 关键词: CSEDI; Testing; Resolution; Deep; Earth

The temperature and composition structure in the Earth's lower mantle provides important clues to the chemical differentiation and dynamics of the planet, especially in regard to how heat is transported from the core to the mantle. A large-scale, slow seismic-velocity anomaly in the lower mantle beneath the Pacific has been imaged in tomographic studies. The thermal and compositional structure of this anomaly remains poorly understood. This research integrates seismological and geodynamical efforts to investigate important issues in understanding the structure of this deep seismic anomaly. We will use thermochemical convection models to develop candidate mantle structures that can be investigated with seismic wave propagation simulations using realistic earthquake and receiver geometries. This will allow us to identify seismic phases that are sensitive to differences between the candidate mantle structures and to investigate whether finite-frequency theory provides additional insight beyond ray-theory for the geometry of these structures, and how 3-D attenuation structure affects our interpretation of tomographic images. This research addresses several challenging problems in understanding the thermal and chemical structure in the Pacific lower mantle through seismic wave propagation in thermo-chemical plume models with focuses on (1) the sensitivity of seismic waves to 3-D variations in temperature and compositional in the lower mantle; (2) the effects of different scaling parameters in translation between temperature and compositional anomalies to seismic wave speed and anelastic attenuation and (3) the resolution limits of current seismic data (including USArray data) and seismic tomographic methods (ray theory and finite-frequency theory) in imaging the structure of the Pacific lower mantle and distinguishing between different plume models including 1) the 'standard' isochemical whole mantle model, with a cluster of narrow plumes under the central Pacific, 2) a thermochemical 'dome' (or pile) under the central Pacific with plumes arising from the interface, and 3) an isolated, sluggish lower mantle with upper mantle derived plumes. Seismological challenges, including quantifying the relative importance of anelastic attenuation and focusing-defocusing effects, and tradeoffs between elastic and anelastic structure will be addressed with full wave propagation simulations in a variety of thermochemical plume models.

地球下地幔的温度和成分结构为地球的化学分异和动力学提供了重要线索，特别是关于热量如何从地核传输到地幔的问题。 层析成像研究对太平洋下地幔中的大规模慢地震速度异常进行了成像。 这种异常现象的热结构和成分结构仍然知之甚少。这项研究整合了地震学和地球动力学的研究成果，旨在研究了解这种深层地震异常结构的重要问题。 我们将使用热化学对流模型来开发候选地幔结构，这些结构可以使用真实的地震和接收器几何形状通过地震波传播模拟进行研究。 这将使我们能够识别对候选地幔结构之间差异敏感的地震相位，并研究有限频率理论是否为这些结构的几何形状提供了超越射线理论的额外见解，以及 3-D 衰减结构如何影响我们对断层扫描图像的解释。这项研究解决了通过热化学羽流模型中的地震波传播来了解太平洋下地幔的热和化学结构的几个具有挑战性的问题，重点是（1）地震波对下地幔温度和成分的三维变化的敏感性； （2）温度和成分异常之间转换的不同尺度参数对地震波速和滞弹性衰减的影响；（3）当前地震数据（包括USArray数据）和地震层析成像方法（射线理论和有限频率理论）对太平洋下地幔结构成像和区分不同地幔柱模型的分辨率限制，包括1）“标准”等化学全地幔模型， 中太平洋下有一群狭窄的地幔柱，2）中太平洋下有一个热化学“圆顶”（或堆），有从界面产生的地幔柱，3）一个孤立的、缓慢的下地幔，有上地幔衍生的地幔柱。 地震学挑战，包括量化非弹性衰减和聚焦-散焦效应的相对重要性，以及弹性和非弹性结构之间的权衡，将通过各种热化学羽流模型中的全波传播模拟来解决。