Collaborative Research: Vertical signatures of lithospheric deformation in the western US

合作研究：美国西部岩石圈变形的垂直特征

• 批准号: 2045291
• 负责人: Kaj Johnson
• 金额: $ 22.16万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2045291&HistoricalAwards=false
• 关键词: Collaborative; Research; Vertical; signatures; lithospheric

Continuous space geodetic observations using GPS and similar constellations allow estimating relative motions of the Earth’s crust, easily down to sub-mm/yr levels. We now have long, 10-20 year GPS records of vertical ground surface motions in the United States with precision levels of 1-2 mm/yr. These precise vertical motions contain important signatures of deformation deep in the Earth. For example, recorded vertical motions close to the subduction zone boundary in the Pacific North-West where the Juan de Fuca plate subducts underneath North America imply that there is a signature of the associated mantle convection processes at depth as well as the process of stick-slip behavior at the plate interface associated with the megathrust earthquake cycle underneath Cascadia. This project will use a range of numerical models and GPS data to capture both the seismic cycle and long-term mantle timescales and work toward disentangling the two. These efforts will help to better understand how the crust deforms and plate boundaries evolve in general, and how the data from Cascadia can be best integrated for a physics-based estimate of seismic hazard in the region. The project engages summer students of UT Austin Jackson School's GeoFORCE program, and with Indiana University’s College of Arts and Sciences Undergraduate Research Experience, which are designed to increase the number of students pursuing STEM degrees. Space geodetic constraints on present-day vertical motions of the crust within the western US are critical for discriminating between competing hypotheses of deformation processes working at various temporal and spatial scales. It has been suggested that small-scale convection signals from the asthenosphere may mask some of the expected signatures of the visco-elastic seismic cycle in Cascadia, for example. This proposed work will use numerical modeling and inversions to disentangle deep-seated and shallow contributions. This research will compare visco-elastic cycle deformation models with visco-plastic mantle flow predictions, and build viscosity models of the mantle in the western US and geodynamic models of long-term deformation with elasto-visco-plastic deformation of the crust and viscous flow in the mantle. The researchers will explore both permanent deformation in the crust as well as transient viscous flow in the mantle and compare with the geodetic velocity field, and also examine deformation at the time scale of the earthquake cycle through kinematic interseismic earthquake cycle models which account for mantle flow due to past earthquakes and interseismic coupling across faults. They will design techniques to integrate results from geodynamic models and kinematic cycle models to obtain a consistent estimate of vertical surface velocities. Such efforts have implications for understanding the tectonic evolution of the United States as well as implications for seismic hazard assessment in the Pacific Northwest.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

使用GPS和类似星座进行连续空间测量学观察，可以估计地壳的相对运动，很容易降至亚MM/YR水平。现在，我们在美国有长期10 - 20年的GPS垂直地面运动记录，精确水平为1-2 mm/年。这些精确的垂直运动包含地球深处变形的重要特征。例如，在太平洋西北部的俯冲区边界附近记录了垂直运动，北美下方的胡安·德福卡板的俯冲俯冲表明，在深度上有相关的地幔连接过程的签名，以及与层面界面与巨质地震周期相关的粘纸界面的过程。该项目将使用一系列数值模型和GPS数据来捕获地震循环和长期地幔时间标准，并致力于解开两者。这些努力将有助于更好地理解地壳变形和板界的一般如何发展，以及如何最好地整合来自Cascadia的数据，从而基于物理学的地震危险估计。该项目与UT Austin Jackson School的Geoforce计划的夏季学生以及印第安纳大学的艺术与科学学院的本科研究经验与夏季学生介入，旨在增加追求STEM学位的学生人数。在美国西部地壳的当今垂直运动上的空间测量限制对于区分在各种临时和空间尺度上工作的变形过程的竞争假设至关重要。有人提出，例如，小圈的小规模转换信号可能掩盖卡斯卡迪亚粘弹性地震循环的某些预期特征。这项拟议的工作将使用数值建模和倒置来解散深处且浅的贡献。这项研究将将Visco弹性循环变形模型与粘性塑料地幔流动预测进行比较，并在美国西部建立地幔的粘度模型和长期变形的地球动力学模型，并用弹性 - Visco-visco-plastic-plastic-plastic-plastic-plastic-plastic-plastic-lastrast-laster colust and colust and colust colust and colust and colust and colust and collastle模型。研究人员将探索地壳中的永久性变形以及地幔中的瞬态粘性流，并与大地速度场进行比较，还可以通过运动次数的地震地震周期在地震周期的时间范围内检查变形，这是由于过去的地震流动而导致的地震流动，这是由于地震流量而导致的地震流动和跨层次的跨地球震动。他们将设计技术以整合地球动力模型和运动学周期模型的结果，以获得垂直表面速度的一致估计。这种努力对理解美国的构造演变以及对西北太平洋危害评估的影响以及对地震危害评估的影响具有影响。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛的影响来通过评估来支持的珍贵支持。