Glacier Seismicity and High Resolution Motion Records: Relation to Glacier Erosion

这是一个大型山地冰川基底过程的多学科研究。冰川是最有效的侵蚀媒介之一。有迹象表明，冰川基底运动直接（可能是线性）相关的侵蚀速率。然而，基础运动是很难评估，在模型以及从观察。最近在阿拉斯加白令冰川附近部署的地震仪为利用现代宽带地震学监测基底过程提供了前所未有的机会。来自这些地震仪的数据正被用来寻找冰川起源的事件，特别是基底源。这些数据由五个冰川观测站的连续记录GPS和一个冰中地震仪补充。GPS记录了三维的冰速度时间序列，将与地震记录相关联。全球定位系统被布置在白令冰川主干道上的平衡线下方，白令冰川从巴格利冰谷流出。冰中地震计与GPS站位于GPS阵列的中心。这个传感器被冻结在冰川表面，在一个几米深的钻孔里，使用蒸汽钻。与GPS布置在一个阵列中，实验的目的是检测是否离散的滑动补丁，整个床滑动事件，或增加冰床应力由于增长的基底空腔导致冰川地震事件。这些机制中的每一种都可能导致基部的不同侵蚀机制。此外，结合地震和冰速度数据可以观察冰川采石。宽带地震仪也允许一些确定的作用，流体在床上，可能表现为谐波震颤。预期的结果将是一个强大的新的数据记录，可用于推导出改进的模型的基础motion.The地震数据来自2005年夏季部署的STEEP（圣埃利亚斯侵蚀/构造项目，由大陆动力学）地震阵列，它已经包围了白令冰川与IRIS/PASSCAL地震网络。STEEP的基本重点是探索侵蚀和构造过程之间的联系，地震网络的建立是为了研究圣埃利亚斯的构造。通过分析该网络内的冰川地震活动，冰川地震研究正在利用地震数据的新结果。在科学上，拟议工作的更广泛影响是通过其与大型多学科STEEP活动的直接联系。这些项目之间的协同作用很大，因为对冰川基础过程的理解是必不可少的。地震数据建立了一个高质量的数据集，这是前所未有的冰川学和增强的全球定位系统数据。该项目由地球物理学和地球物理学研究所地貌学和土地利用动态方案资助。

This is a multi-disciplinary study of basal processes on a large mountain glacier. Glaciers are among the most effective agents of erosion. There are indications that glacier basal motion is directly (maybe linearly) related to erosion rates. Yet, basal motion is difficult to assess, in models as well as from observations. A recent deployment of seismometers near the Bering Glacier, Alaska, is offering an unprecedented opportunity to monitor basal processes with modern broadband seismology. Data from these seismometers is being used to look for events of glacial origin, and in particular basal sources. These data are supplemented by five glacier stations of continuously recording GPS and an in-ice seismometer. The GPS are recording an ice velocity timeseries in 3-d that will be correlated with the seismic records. The GPS are laid out in an array just below the equilibrium line on the main trunk of the Bering Glacier where it drains from the Bagley Ice Valley. The in-ice seismometer is co-located with the GPS station at the center of the GPS array. This sensor is frozen into the surface of the glacier, in a borehole several meters deep, made using a steam drill. With the GPS laid out in an array, the experiment is designed to detect whether discrete slip patches, whole bed sliding events, or increasing ice-bed stresses due to the growth of basal cavities lead to glacial seismic events. Each of these mechanisms may contribute to different mechanisms of erosion at the base. Moreover, the combined seismic and ice velocity data may allow observation of glacial quarrying. Broadband seismometers also allow some determination of the role of fluids at the bed, possibly manifest as harmonic tremor. The expected outcome will be a powerful new data record that may be used to derive improved models of basal motion.The seismic data come from the summer 2005 deployment of the STEEP (St. Elias Erosion/tectonics Project, funded by Continental Dynamics) seismic array, which has surrounded the Bering Glacier with an IRIS/PASSCAL seismic network. The basic focus of STEEP is to explore the links between erosion and tectonic processes, and the seismic network was built to study tectonics in the St. Elias. By analyzing glacier seismicity within this network, the glacier seismic study is leveraging new results from the seismic data. Scientifically, the broader impacts of the proposed work are through its direct link to the large multi-disciplinary STEEP activity. The synergies between these projects are large, because an understanding of glacier basal processes is essential. The seismic data establishes a high quality data set that is unprecedented in glaciology and that is enhanced by the GPS data. This project is funded by Geophysics and the EAR Geomorphology and Land-Use Dynamics Program.