Collaborative Research: Dynamics of Crust-Mantle Coupling through Combined Analysis and Modeling of EarthScope Seismic, Geodetic, and Geologic Data

合作研究：通过 EarthScope 地震、大地测量和地质数据的组合分析和建模研究壳幔耦合动力学

• 批准号: 1053292
• 负责人: James Davis
• 金额: $ 21.84万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-15 至 2014-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1053292&HistoricalAwards=false
• 关键词: Collaborative; Research; Dynamics; Crust; Mantle

This collaborative research effort is integrating seismological, geodetic, and geological information from EarthScope to investigate hypotheses regarding the present-day structure and evolution of the Great Basin region of the western United States. Initial discoveries enabled by the EarthScope program and prototype studies in this region have led to new and potentially related hypotheses that echo prominent research themes in observational and theoretical dynamics of the continents and their margins: (1) the evolution and control of subducting slabs on the mantle flow field, (2) the stability of the lower lithosphere against convective loss, and (3) the nature and extent of subhorizontal decoupling horizons within the lithosphere. The primary motivation for the current is the need to reconcile recent geophysical, geodetic, and geological findings in the Great Basin region directly related to these themes. Beneath the central Great Basin, seismic imaging reveals a cylindrical mass of higher than average wavespeeds east of the actively subducting Juan de Fuca plate near the zone of weakest azimuthal anisotropy in the western United States, along with a swirl-like pattern of fast polarization directions. When considered with other regional geophysical and geologic patterns, hypotheses that may explain these observations include mantle flow around a lithospheric keel, toroidal flow driven by the sinking of the Juan de Fuca slab, mantle downwelling driven by a lithospheric drip, and a number of other possibilities. Recent geodetic data for the Great Basin reveal transient changes in geodetic velocities, which when considered with other local geologic patterns, are consistent with the hypothesis that an active decoupling horizon exists, perhaps localized along the Moho or some other deep decoupling zone beneath the Great Basin. Further, relative to a dynamic model that matches Quaternary rates and orientations of deformation, a time-averaged strain rate solution obtained from campaign and continuous GPS shows a contractional dilatation anomaly in the same vicinity as the geodetic and seismic anomalies.The collocation of such a broad range of geophysical, geodetic, and geologic anomalies beneath the broadly extending Great Basin is unlikely to be coincidental, yet combined they defy conventional models of a classic extensional tectonic regime like the Great Basin. Understanding the relationship between these processes through a comprehensive series of hypothesis testing can transform our general insight of lithospheric dynamics. This project is focused on conducting a comprehensive suite of new investigations to test hypotheses focused on linkages between mantle flow, lithospheric decoupling, and lithospheric destabilization for the Great Basin region. This effort is utilizing new results developed through analyses of EarthScope USArray Transportable Array (TA), EarthScope Plate Boundary Observatory (PBO), and EarthScope Geology data. Specific datasets include seismic imaging (tomography, anisotropy, and receiver functions), continuous GPS, seismotectonics, and patterns of historic and late Quaternary seismic strain release in the upper crust. Results from these analyses will provide the required data for a series of new 3-D and 4-D numerical models developed within this project. This research is inherently integrative, and thus constitutes an important opportunity to combine results from different components of the EarthScope program for a tectonic setting that historically is among the best known and most enigmatic in the world. From a broader impacts perspective, this project represents a new multidisciplinary effort combining four separate Earth science disciplines to draw recent EarthScope-enabled discoveries into a holistic view of Great Basin evolution. Data collected and analyzed for this project will be distributed publicly to the scientific community. The project is enabling the training of several young scientists in multidisciplinary research. The PIs are coordinating with the EarthScope National Office and IRIS to provide findings and discoveries from this project in several forms, including an IRIS Active Earth module that looks into the Basin and Range from the surface through the upper mantle and will serve as an illustration of how continental-scale tectonic forces shape present-day surface deformation and deeper dynamics.

这项合作研究工作是将地震，地球学和地质信息整合到地球景观中，以研究有关西部大盆地地区目前的结构和演变的假设。该地区的Earthscope计划和原型研究能够实现的最初发现，导致了新的且可能相关的假设，这些假设与大陆的观察和理论动态有关的重要研究主题呼应了及其边缘的观察和理论动力学：（1）在地幔流场上俯冲平板的演变和控制，层层损失的稳定性，（2）（2）（2）（2）（2）3（2）3（2）3（2）3（2）3（2）3（2）3（2）（3）岩石圈内的地平线。 当前的主要动机是需要调和与这些主题直接相关的伟大盆地地区最近的地球物理，地质和地质发现。在中央大盆地的基础下，地震成像揭示了在美国西部最弱的方位角各向异性区域附近积极俯冲的Juan de fuca板的高于平均波动的圆柱质量，以及快速极化方向的漩涡状图案。当与其他区域地球物理和地质模式一起考虑时，可以解释这些观察结果的假设包括围绕岩石圈龙骨的地幔流，由Juan de Fuca板的下沉驱动的环形流动，地幔下的地面下的底层下层，由岩石圈滴利料驱动，以及其他可能性。大盆地的最新测量数据揭示了大地速度的短暂变化，当与其他局部地质模式一起考虑时，这与假设存在于Moho或其他一些深层解耦区的假设是一致的。此外，相对于与四季度速率和变形的方向相匹配的动态模型，从运动和连续GPS获得的时间平均应变率解决方案显示出与地球和地震异常相同的收缩扩张异常。巧合，但结合在一起，他们反抗了像大盆地这样经典的延伸构造政权的传统模型。通过一系列全面的假设检验了解这些过程之间的关系可以改变我们对岩石圈动力学的一般见解。该项目的重点是进行一系列新的研究，以测试集中在大盆地地区地幔流，岩石圈解耦和岩石圈不稳定之间的联系的假设。这项工作正在利用通过分析Earthscope USArray可运输阵列（TA），Earthscope Plate Barge Boundarevatory（PBO）和Earthscope地质数据而开发的新结果。特定的数据集包括地震成像（断层扫描，各向异性和接收器功能），连续的GPS，地震仪以及上皮中历史悠久和晚期季震菌株释放的模式。这些分析的结果将为本项目中开发的一系列新的3-D和4-D数值模型提供所需的数据。这项研究本质上是综合性的，因此构成了将Earthscope计划不同组成部分的结果结合起来的重要机会，用于构造环境，历史上是世界上最著名和最神秘的。从更广泛的影响角度来看，该项目代表了一项新的多学科努力，结合了四个独立的地球科学学科，以将最新的基于地球史的发现吸引到大盆地进化的整体视野中。为该项目收集和分析的数据将公开分发给科学界。该项目正在使几位年轻科学家在多学科研究中进行培训。 PI与Earthscope国家办公室和IRIS进行了协调，以多种形式从该项目中提供发现和发现，包括虹膜活跃的地球模块，该模块从盆地和从表面到上地幔范围不等，并将用作大陆尺度的构造力量的形状形状的表面表面变形和更深的动力学。