Geodetic constraints on the mechanism of glacial earthquakes

首席调查员请求支持将于2006年夏天在东格陵兰岛的赫尔海姆冰川进行实地试验的研究，以了解冰川地震的产生机制及其与冰川学和气候学过程的关系。2003年，Ekstrom在阿拉斯加、南极洲和格陵兰岛的冰川上发现了一种新的地震类型。远震分析表明，这些冰川地震是冰川冰在冰川床上快速滑动的结果。人们对冰川地震发生的机制知之甚少，但最近的观察表明，这与冰川和冰盖的水文循环有关。格陵兰岛上发生的地震数量具有强烈的季节性调节，最多的事件发生在夏末的几个月。自大约2000年以来，格陵兰各地出口冰川的地震数量迅速增加，这表明与大规模气候变化有关。这项研究由两部分组成：1)在Helheim冰川上部署全球定位系统(GPS)站，以获得与冰川地震相关的位移瞬变的直接测量，其后勤费用将单独提供资金；2)利用每个领域的最先进技术，对记录的GPS、地震和冰川学数据进行跨学科的综合分析，以了解冰川地震发生的机制。地震分析将提供对震源特征的长期估计，而大地观测将提供有关冰川内变形的时间和模式的详细信息。对这些数据集的联合分析将产生变形过程的地球物理一致的模型，然后将在对背景冰川行为和随时间变化的融化速率的冰川学观测的背景下进行研究，以评估表面融化与冰川地震产生有关的假设。智力上的功绩。这项研究将极大地提高对冰川地震控制过程的理解，冰川地震是一种以前未知的地球物理现象。它还将提供对冰川变形模式的洞察，以及冰川地震活动与全球气候变化之间可能的联系。更广泛的影响。除了大地测量仪和地震学家外，这一结果对冰川学家和气候学家也很重要。这项研究的结果是对冰川地震的理解，这将使遥感地震数据能够被用作冰川学工具和研究全球变化，同时也有助于增进对固体地球对地球表面或其附近的瞬时变形事件的反应的了解。

NettlesOPP-0612609The Principal Investigators request support for research to be carried out with a pilot field experiment in summer, 2006 at Helheim Glacier, East Greenland to obtain an understanding of the mechanisms by which glacial earthquakes are generated and their relation to glaciological and climatological processes. A new class of earthquakes occurring at glaciers in Alaska, Antarctica, and Greenland was identified in 2003 by Ekstrom. Teleseismic analysis indicates that these glacial earthquakes are the result of rapid sliding of the glacial ice over the glacier bed. Little is understood about the mechanism by which glacial earthquakes occur, but recent observations indicate a relationship with the hydrological cycle at glaciers and ice sheets. The number of earthquakes that occur on Greenland is strongly seasonally modulated, with the largest number of events occurring during the late summer months. A rapid increase in the number of earthquakes at outlet glaciers across Greenland since approximately 2000 suggests a link to large-scale climate change. This research consists of two parts: 1) a field deployment of Global Positioning System (GPS) stations on Helheim Glacier to obtain direct measurements of the displacement transients associated with glacial earthquakes, the logistical costs for which will be funded separately; and 2) integrated, interdisciplinary analysis of recorded GPS, seismic, and glaciological data using state-of-the-art techniques from each field to obtain an understanding of the mechanism by which glacial earthquakes occur. Seismic analyses will provide long-wavelength estimates of the earthquake source characteristics, while the geodetic observations will provide detailed information about the timing and pattern of deformation within the glacier. A combined analysis of these datasets will result in geophysically consistent models of the deformation process, which will then be studied in the context of glaciological observations of the background glacier behavior and time-varying melting rates to evaluate the hypothesis that surface melting is linked to the generation of glacial earthquakes. Intellectual Merit. This research will lead to a greatly improved understanding of the processes controlling glacial earthquakes, a previously unknown geophysical phenomenon. It will also provide insight into modes of glacier deformation and possible connections between glacial earthquake activity and global climate change. Broader Impacts. The results will be important for glaciologists and climatologists in addition to geodesists and seismologists. The understanding of glacial earthquakes developed as a result of this study will allow remote-sensing seismic data to be used as a glaciology tool and studies of global change, while also leading to improved knowledge of the response of the solid Earth to transient deformation events at or near the surface of the Earth.