Geodetic constraints on the mechanism of glacial earthquakes

主要研究人员要求支持2006年夏季在东格陵兰岛Helheim冰川进行的试点实地实验，以了解冰川地震产生的机制及其与冰川学和气候过程的关系。2003年，埃克斯特罗姆确定了发生在阿拉斯加、南极洲和格陵兰岛冰川上的一种新的地震类型。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，但最近的观测表明，冰川和冰盖的水文循环与地震有关。格陵兰岛发生地震的次数具有强烈的季节性变化，在夏末的几个月里发生的地震次数最多。大约自2000年以来，格陵兰岛出口冰川的地震次数迅速增加，这表明地震与大规模气候变化有关。本研究包括两个部分：1)在Helheim冰川上实地部署全球定位系统（GPS）站点，获取与冰川地震相关的位移瞬态的直接测量数据，其后勤费用将单独资助；2)利用各领域最先进的技术，对记录的GPS、地震和冰川学数据进行综合、跨学科的分析，以了解冰川地震发生的机制。地震分析将提供震源特征的长波长估计，而大地测量观测将提供关于冰川内变形的时间和模式的详细信息。对这些数据集的综合分析将得出地球物理上一致的变形过程模型，然后将在冰川背景行为和随时间变化的融化速率的冰川学观测的背景下对其进行研究，以评估地表融化与冰川地震产生有关的假设。知识价值。这项研究将大大提高对控制冰川地震的过程的理解，这是一种以前未知的地球物理现象。它还将深入了解冰川变形的模式，以及冰川地震活动与全球气候变化之间的可能联系。更广泛的影响。除了大地测量学家和地震学家之外，这些结果对冰川学家和气候学家也很重要。对冰川地震的理解将使遥感地震数据能够用作冰川学工具和全球变化研究，同时也有助于提高对固体地球对地球表面或其附近瞬态变形事件的响应的认识。

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.