Collaborative Research: Characterizing Brittle Failure and Fracture Propagation in Fast Ice Sliding with Dynamic Rupture Models based on Whillans Ice Stream Seismic/Geodetic Data

合作研究：利用基于 Whillans 冰流地震/大地测量数据的动态破裂模型来表征快速冰滑动中的脆性破坏和断裂扩展

• 批准号: 1542885
• 负责人: Eric Dunham
• 金额: $ 21万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1542885&HistoricalAwards=false
• 关键词: Collaborative; Research; Characterizing; Brittle; Failure

This project investigates a rapidly moving section of the West Antarctic Ice Sheet known as the Whillans Ice Stream. Ice streams and outlet glaciers are the major pathways for ice discharge from ice sheets into the ocean. Consequently, understanding ice stream dynamics, specifically the processes controlling the frictional resistance of ice sliding on sediments at its base, is essential for predictive modeling of how Earth's ice sheets will respond to a changing climate. Rather than flowing smoothly, Whillans Ice Stream advances in stick-slip cycles: brief periods of rapid sliding, equivalent to magnitude 7 earthquakes, alternating with much longer periods of repose. The PIs will perform simulations of these stick-slip cycles using computer codes originally developed for modeling tectonic earthquakes. By matching observed ice motions, the PIs will constrain the range of frictional processes acting at the base of the ice stream. An additional focus of the project is on brittle fracture processes in ice, expressed through seismic waves radiated by faulting and/or crevassing episodes that accompany the large-scale sliding events. An understanding of ice fracture provides a basis for assessing the susceptibility of ice shelves to rifting and catastrophic disintegration. Project results will be incorporated into outreach activities (from elementary school to community college events) as well as a polar science class for the California State Summer School for Mathematics and Science (COSMOS) program for high school students.Simulations of the stick-slip cycle will employ 3D dynamic rupture models that simultaneously solve for the seismic wavefield and rupture process, consistent with elastodynamic material response and friction laws on the ice stream bed. Stresses and frictional properties will be varied to achieve consistency with surface GPS and broadband seismic data as well as borehole seismograms from the WISSARD project. The results will be interpreted using laboratory till friction experiments, which link velocity-weakening/strengthening behavior to temperature and water content, and to related experiments quantifying basal drag from ice flow over rough beds. The source mechanism of seismicity accompanying the slip events (shear faulting versus crevassing) will be determined using 3D waveform modeling in conjunction with mechanical models of the seismic source processes. This proposal does not require fieldwork in the Antarctic.

该项目调查了南极冰盖迅速移动的部分，称为Whillans冰流。冰流和出口冰川是从冰盖进入海洋的主要途径。因此，了解冰流动力学，特别是控制冰块在其基部沉积物上滑动的摩擦阻力的过程，对于预测地球冰盖将如何应对气候变化的响应至关重要。 Whillans冰流并没有顺利地流动，而是在棒状滑移循环中进展：快速滑动的短期，相当于7级地震，与更长的安息时间交替。 PI将使用最初用于建模构造地震开发的计算机代码对这些粘性循环进行模拟。通过匹配观察到的冰运动，PI将限制作用在冰流底部的摩擦过程的范围。该项目的另一个重点是冰中的脆性断裂过程，这些过程是通过大规模滑动事件伴随的断层和/或曲面发作辐射的地震波表示的。对冰骨折的理解为评估冰架裂解和灾难性瓦解的敏感性提供了基础。 Project results will be incorporated into outreach activities (from elementary school to community college events) as well as a polar science class for the California State Summer School for Mathematics and Science (COSMOS) program for high school students.Simulations of the stick-slip cycle will employ 3D dynamic rupture models that simultaneously solve for the seismic wavefield and rupture process, consistent with elastodynamic material response and friction laws on the ice stream bed.应力和摩擦特性将有所不同，以与Wissard Project的表面GP和宽带地震数据以及井眼地震图达到一致性。结果将使用实验室进行解释，直到摩擦实验，该实验将速度的/加强行为与温度和水的含量联系起来，并与相关的实验量化了从冰流中的基础阻力量化在粗糙的床上。伴随滑动事件（剪切断层与缝隙）的地震性的来源机制将使用3D波形建模与地震源过程的机械模型结合使用。 该提案不需要南极的现场工作。