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: 1543187
• 负责人: Susan Schwartz
• 金额: $ 3.99万
• 依托单位: University of California-Santa Cruz
• 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 2019-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1543187&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.

该项目调查了西南极冰盖的一个快速移动的部分，称为Whillans冰流。冰流和出口冰川是冰从冰盖排入海洋的主要通道。因此，了解冰流动力学，特别是控制冰在其底部沉积物上滑动的摩擦阻力的过程，对于预测地球冰盖如何应对气候变化的建模至关重要。而不是平稳流动，Whillans冰流在粘滑周期中前进：短暂的快速滑动，相当于7级地震，与更长的静止期交替。PI将使用最初为模拟构造地震而开发的计算机代码来模拟这些粘滑周期。通过匹配观测到的冰运动，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，通过伴随大规模滑动事件的断层和/或裂缝事件辐射的地震波来表达。冰破裂的理解提供了一个基础，评估冰架断裂和灾难性解体的敏感性。项目成果将纳入外联活动（从小学到社区大学的活动）以及加州州立数学与科学暑期学校（COSMOS）高中生项目的极地科学课。粘滑循环的模拟将采用三维动态破裂模型，同时解决地震波场和破裂过程，与冰河床上的弹性动力学材料响应和摩擦定律一致。应力和摩擦特性将有所不同，以便与地面GPS和宽带地震数据以及WISSARD项目的钻孔地震图保持一致。结果将解释使用实验室直到摩擦实验，连接速度减弱/加强行为的温度和含水量，并量化从粗糙的床冰流的基础阻力的相关实验。伴随滑动事件（剪切断层与裂隙）的地震活动的震源机制将使用三维波形建模结合震源过程的力学模型来确定。 这项提议不需要在南极进行实地考察。