Collaborative Research: Ten years later: Resolving the postseismic deformation processes of the 2002 Denali Fault earthquake

合作研究：十年后：解决 2002 年德纳利断层地震的震后变形过程

• 批准号: 1417291
• 负责人: Jeffrey Freymueller
• 金额: $ 36.67万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1417291&HistoricalAwards=false
• 关键词: Collaborative; Research; Ten; years; later

The Earth's response to large earthquakes does not end when the seismic shaking dies away. Large earthquakes substantially change forces (stresses) within the Earth, and by measuring and modeling the response to these changes, we can learn about the mechanical properties of deep fault zones and the material that surrounds them. This time-dependent and transient response of the Earth produces postseismic deformation, which we will measure using high-precision GPS. A key challenge of postseismic deformation studies is to separate the effects of the two main mechanisms, afterslip or continued slip on the deep fault plane, and viscoelastic relaxation within the mantle and/or lower crust. In the first few years after the earthquake, these two mechanisms can produce similar deformation at the surface of the Earth, but they decay with time at different rates. In this project, we will use a long record of data (up to 15 years) following the 2002 Denali fault earthquake to develop a complete model for the postseismic deformation following this earthquake. This improved mechanical model will allow us to better understand the forces that drive tectonic deformation in Alaska, and the interaction between earthquakes.We will carry out GPS surveys of a dense network of sites surrounding the 2002 fault rupture. These data will provide important spatial resolution to complement the sparse continuous GPS network from the Plate Boundary Observatory, which provides critical information about the time evolution of the postseismic deformation. We will carefully examine the observed deformation to identify observations that can be explained entirely or mostly by a single postseismic mechanism, if possible, which makes it easier to constrain model parameters. We will recalculate a new coseismic slip distribution using a finite element code that can utilize the full 3-D inferred elastic Earth structure, including the subducting slab, so that we can most accurately compute the postseismic response to the slip. We will develop 3D finite element models and other models to explain the observed deformation, and evaluate how these models would respond to other stress changes like the 1964 earthquake, or glacial unloading. We will share information about the Denali fault, earthquakes in Alaska, and the results of this project with the public through interaction with Denali National Park. The Park hosts about 400,000 visitors each year and coordinated outreach efforts with the Park offer a chance to reach a broad audience.

当地震摇晃消失时，地球对大地震的反应不会结束。大地震实质上改变了地球内部的力（应力），通过测量和建模对这些变化的响应，我们可以了解深层断层区域的机械性能以及周围的材料。地球的时间依赖性和瞬态响应会产生地震后变形，我们将使用高精度GPS进行测量。后视性变形研究的一个主要挑战是将两种主要机制的影响分开，滑道后或持续滑动在深层断层平面上，以及地幔内和/或下层地壳内的粘弹性松弛。在地震发生后的头几年，这两种机制可以在地球表面产生相似的变形，但是它们会随着时间的流逝而以不同的速度衰减。在这个项目中，我们将在2002年Denali断层地震后使用较长的数据记录（长达15年），以开发此地震后的后视后变形的完整模型。这种改进的机械模型将使我们能够更好地理解驱动阿拉斯加构造变形的力，以及地震之间的相互作用。我们将对2002年断层破裂的地点密集网络进行GPS调查。这些数据将提供重要的空间分辨率，以补充板边界观测站的稀疏连续GPS网络，该网络提供了有关后震后变形时间演变的关键信息。我们将仔细检查观察到的变形，以确定可以通过单一的后震后机制来解释的观测值，如果可能的话，这使得更容易约束模型参数。我们将使用有限的元件代码来重新计算新的Coseissic滑动分布，该元件代码可以利用完整的3-D推断弹性地球结构（包括俯冲板），以便我们可以最准确地计算出对滑动的后观点响应。我们将开发3D有限元模型和其他模型来解释观察到的变形，并评估这些模型将如何应对其他应力变化，例如1964年地震或冰川卸载。我们将通过与Denali国家公园的互动，分享有关Denali断层，阿拉斯加地震的信息以及该项目的结果。该公园每年有约40万名游客，与公园协调宣传工作为吸引广泛的观众提供了机会。