Imaging the Fine Structure of Earthquakes and Faults with High-Precision Aftershocks

利用高精度余震对地震和断层的精细结构进行成像

• 批准号: 1520680
• 负责人: Felix Waldhauser
• 金额: $ 29.8万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-11-01 至 2019-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1520680&HistoricalAwards=false
• 关键词: Imaging; Fine; Structure; Earthquakes; Faults

The geometry and structure of active faults, breaks in the Earth's crust along which movement takes place during an earthquake, are believed to play a controlling part in how earthquakes start, how big they become, and how they stop. Only where faults break the Earth's surface can we study the zones of active faulting directly; the rest, and often more complex part of the fault is buried deep underground. This project studies the fine-scale details of the structure and geometry of fault zones at crustal depths using aftershocks of larger earthquakes in California. Using highly accurate locations of aftershocks along faults that just broke in big earthquakes, the internal makeup of fault zones can be imaged at the meter scale. This will enable detailed studies of fault features such as the thickness of damage zones and irregularities in the fault surface, which are essential for understanding how faults work and which factors control the evolution of rupture.The characterization of three-dimensional fault zone structure and its evolution is essential for understanding how faults work and which factors control the evolution of rupture. This project studies the ultra-fine, three-dimensional structure of active faults in California, how it evolves with fault maturity, and how it ultimately governs the initiation, propagation, and termination of earthquakes. Geological studies of fault outcrops have provided a generalized and highly simplified, one-dimensional picture of faults in which the fault core, including the principal slip surface(s), is surrounded by a damage zone of fractured rock. In three dimensions faults appear to be much more complex and a complete description of them, even an idealized one, does not exist. This project?s main goal is a systematic and comparative analysis of over 150,000 high-precision aftershock locations and additional parameters associated with 78 large (M ≥ 5.5) strike-slip and thrust earthquakes in California that have the resolution power to image the internal structure and properties of fault zones at the scale of tens of meters or better. These data are used to investigate the evolution of fault zone structure with fault maturity, and to measure features of fault maturity such as the evolution of the smoothness of the fault and growth (or shrinkage) of the damage zone with fault displacement. We expect this study to recognize common factors in the fine structure of these faults and the earthquakes that occurred on them as well as how these features change with fault maturity. Furthermore, fault segmentation, jogs, and step overs will be characterized and their role in the nucleation and arrest of rupture as well as in fault growth and interaction investigated.

活动断层的几何形状和结构被认为对地震如何开始、发展到多大以及如何停止起着控制作用。活动断层是地壳上的断裂，地震发生时沿着这些断裂发生运动。只有在断裂打破地球表面的地方，我们才能直接研究活动断裂带；断层的其余部分，通常是更复杂的部分，深埋在地下。这个项目利用加利福尼亚大地震的余震研究地壳深处断层带的结构和几何形状的精细细节。利用高精确度的余震位置，沿着刚刚在大地震中断裂的断层，断层带的内部构成可以在米尺度上成像。这将有助于详细研究断层特征，如损伤带的厚度和断层表面的不规则性，这对于理解断层如何工作以及哪些因素控制破裂的演变至关重要。三维断裂带结构及其演化的表征对于理解断裂的工作原理和控制断裂演化的因素至关重要。本项目研究加州活动断层的超精细三维结构，研究其随断层成熟如何演变，以及最终如何支配地震的发生、传播和终止。断层露头的地质研究提供了一种广义的、高度简化的、一维的断层图像，其中断层核，包括主滑动面，被破碎岩石的破坏带所包围。在三维空间中，断层似乎要复杂得多，对它们的完整描述，甚至是理想化的描述，都是不存在的。这个项目吗?该中心的主要目标是对加利福尼亚的78次大型（M & & & #8805; 5.5）走滑和逆冲地震的15万多次高精度余震位置和附加参数进行系统的比较分析，这些地震具有在几十米或更高的尺度上对断层带的内部结构和性质进行成像的分辨率。这些数据用于研究断层成熟度变化对断裂带结构的影响，以及断层平滑度的变化和断层位移对破坏带生长（或收缩）的影响等断层成熟度特征。我们期望这项研究能够认识到这些断层的精细结构和发生在这些断层上的地震的共同因素，以及这些特征如何随着断层的成熟而变化。此外，断层分割、滑动和台阶将被表征，并研究它们在破裂成核和阻止以及断层生长和相互作用中的作用。