Seismic Imaging of Alaska Using Spectral-Element and Adjoint Methods

使用谱元和伴随方法对阿拉斯加进行地震成像

• 批准号: 1215959
• 负责人: Carl Tape
• 金额: $ 28.59万
• 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: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1215959&HistoricalAwards=false
• 关键词: Seismic; Imaging; Alaska; Using; Spectral; Seismic; Imaging; Alaska; Using; Spectral

This project will apply spectral-element and adjoint methods to develop a three-dimensional seismic reference model for the crust and uppermost mantle of Alaska. Finite-frequency surface waves and body waves will be extracted from full seismic waveforms in order to provide the greatest resolution for seismic imaging. Major sedimentary basins will be incorporated within the initial three-dimensional models by using existing information such as gravity data and industry seismic data. A new catalog of seismic moment tensors will be constructed by inverting measurements of body waves and surface waves for earthquake depth and radiation pattern.Active tectonic settings exhibit deformation in the form of earthquakes, geodetic strain rate, erosion, and sedimentation. On longer time scales, these processes create a highly heterogeneous crustal composition. For example, faults may offset two distinct rock types, or a basin may open and accumulate kilometer-thick layers of sediment. On shorter time scales, these settings experience abundant earthquakes in response to stresses within the crust. By using these abundant earthquakes, seismic imaging with accurate numerical methods can reveal the extreme complexity within active tectonic settings. Spectral-element methods have been used to model wave propagation in complex geological settings, such as those with strong topographic variations and sedimentary basins. The accuracy of these wave propagation methods can be embedded in an adjoint inverse problem to improve subsurface images of Earth's crust. The primary product will be a three-dimensional reference model for Alaska. This model will describe the spatial variations in compressional wave speed, shear wave speed, and density in Alaska. The quality of the model will be highest in the crust, and it will provide opportunities for larger-scale tomographic studies of the entire subduction and collisional setting. The reference model will be useful as a framework for the upcoming GeoPRISMS focus in Alaska as well as the anticipated EarthScope Transportable Array.

该项目将采用光谱元素和伴随方法来开发阿拉斯加地壳和最高地幔的三维地震参考模型。有限频率的表面波和体波将从全地震波形中提取，以提供地震成像的最大分辨率。主要的沉积盆地将通过使用重力数据和行业地震数据等现有信息来纳入最初的三维模型。通过对地震深度和辐射模式的体波和表面波的倒数测量，将构建一个新的地震力矩收纪录目录。活动性构造设置以地震，大地测量应变速率，侵蚀和沉积物的形式表现出变形。在较长的时间尺度上，这些过程产生了高度异质的地壳组成。例如，故障可能会抵消两种不同的岩石类型，或者盆地可能会打开并积聚公里厚的沉积物层。在较短的时间尺度上，这些设置经历了大量地震，以应对地壳内的压力。通过使用这些丰富的地震，具有准确的数值方法的地震成像可以揭示主动构造设置内的极端复杂性。光谱 - 元素方法已用于模拟复杂地质环境中的波浪传播，例如具有强大的地形变化和沉积盆地的传播。这些波传播方法的准确性可以嵌入到伴随问题中，以改善地球地壳的地下图像。主要产品将是阿拉斯加的三维参考模型。该模型将描述阿拉斯加压缩波速，剪切波速度和密度的空间变化。该模型的质量将在外壳中最高，它将为整个俯冲和碰撞环境的大规模断层扫描研究提供机会。该参考模型将作为即将在阿拉斯加以及预期的可运输阵列的地理选址的框架中有用。