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

这个项目调查了南极西部冰盖快速移动的部分，被称为惠兰斯冰流。冰流和出水口冰川是冰原向海洋排放冰的主要途径。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，对于地球冰盖如何应对气候变化的预测建模至关重要。惠兰斯冰流不是平稳流动的，而是以粘滑循环的方式前进：短暂的快速滑动，相当于7级地震，与更长的静止期交替进行。pi将使用最初为构造地震建模而开发的计算机代码对这些粘滑循环进行模拟。通过与观测到的冰运动相匹配，pi将限制在冰流底部作用的摩擦过程的范围。该项目的另一个重点是研究冰的脆性断裂过程，通过伴随着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。对冰断裂的理解为评估冰架对裂谷和灾难性崩解的敏感性提供了基础。项目成果将纳入推广活动（从小学到社区大学活动），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程。粘滑循环的模拟将采用三维动态破裂模型，同时求解地震波场和破裂过程，与冰河床上的弹性动力材料响应和摩擦规律一致。应力和摩擦特性将发生变化，以与地面GPS和宽带地震数据以及来自WISSARD项目的井眼地震图保持一致。结果将使用实验室摩擦实验来解释，该实验将速度减弱/强化行为与温度和含水量联系起来，并与相关实验量化粗糙床上冰流的基础阻力。伴随滑动事件的地震活动性的源机制（剪切断层与裂缝）将使用三维波形建模与地震源过程的力学模型相结合来确定。这项建议不需要在南极进行实地考察。

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.