Dynamics of stick-slip motion, Whillans Ice Stream, Antarctica
Dynamics of stick-slip motion, Whillans Ice Stream, Antarctica
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南极洲威兰斯冰流的粘滑运动动力学
DOI：
10.1016/j.epsl.2011.02.052
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发表时间：
2011
影响因子：
5.3
通讯作者：
K. Christianson
中科院分区：
文献类型：
--
作者：
J. P. Winberry;S. Anandakrishnan;D. Wiens;R. Alley;K. Christianson
西南极洲Whillans冰流（WIS）的粘滑运动和相关的地震辐射是最近对冰盖意外行为的许多观测中的两个，这些行为正在挑战冰川快速运动的传统模型。在这里，我们发现，WIS滑动事件反复从位于冰流中间的粘性点成核，类似于传统地震物理模型中的粗糙体。在滑动期间，该区域的运动比周围地区少，因此，应力集中，并在滑动开始时产生地震能量脉冲。传播破裂突破了冰流北方的一个额外的粗糙体，在开始后6-12分钟产生另一个地震能量脉冲。这两个凸体都是比周围区域具有更高水力势的区域，这表明它们可能由于水润滑减少而具有更大的床摩擦。潮汐起搏的应力积累结合故障愈合控制施加的应力在故障时，与更高的应力给出更快的传播的破裂前和更高的滑动速度，这些差异反映在时间的破裂到达。我们的研究结果强调了大冰流对外部强迫的微小变化的高度敏感性，以及冰下床有限区域在控制其运动中的重要性，并为重复地震的力学提供了见解。
The stick–slip motion and associated seismic emissions of Whillans Ice Stream (WIS), West Antarctica are two of the many recent observations of unexpected ice sheet behavior that are challenging traditional models of rapid glacier motion. Here we find that the WIS slip events repeatedly nucleate from a sticky-spot located in the middle of the ice stream, acting similar to an asperity in traditional models of earthquake physics. This region shows less motion than surrounding areas during the inter-slip periods, thus, concentrating stress and producing a pulse of seismic energy at the onset of slip. The propagating rupture breaks through an additional asperity in the northern part of the ice stream, producing another pulse of seismic energy 6–12 min after initiation. Both asperities are regions of higher hydraulic potential than surrounding regions, suggesting they may have greater bed friction due to reduced water lubrication. Tidal pacing of the stress accumulation combined with fault healing controls the applied stress at failure, with higher stress giving faster propagation of the rupture front and higher slip velocities; these differences are reflected in the timing of the teleseismic arrivals. Our results highlight both the great sensitivity of large ice streams to small changes in external forcing and the importance of limited regions of the subglacial bed in controlling their motion, as well as providing insights to the mechanics of repeating earthquakes.