• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Seismological research letters >Experimental Evidence of Velocity‐Weakening Friction during Ice Slip over Frozen Till: Implications for Basal Seismicity in Fast Moving, Soft‐Bed Glaciers and Ice Streams
【24h】

Experimental Evidence of Velocity‐Weakening Friction during Ice Slip over Frozen Till: Implications for Basal Seismicity in Fast Moving, Soft‐Bed Glaciers and Ice Streams

机译：Experimental Evidence of Velocity‐Weakening Friction during Ice Slip over Frozen Till: Implications for Basal Seismicity in Fast Moving, Soft‐Bed Glaciers and Ice Streams

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相关主题

摘要

Observations of glacier slip over till beds, across a range of spatial and temporal scales, show abundant seismicity ranging from Mw∼−2 microearthquakes and tremor (submeter asperities and millisecond duration) to Mw∼7 slow‐slip events (⁠∼50  km rupture lengths and ∼30  min durations). A complete understanding of the mechanisms capable of producing seismic signals in these environments represents a strong constraint on bed conditions. In particular, there is a lack of experimental confirmation of velocity‐weakening behavior of ice slipping on till, where friction decreases with increasing velocity—a necessity for nucleating seismic slip. To measure the frictional strength and stability of ice sliding against till, we performed a series of double‐direct‐shear experiments at controlled temperatures slightly above and below the ice melting point. Our results confirm velocity‐strengthening ice–till slip at melting temperatures, as has been found in the few previous studies. We provide best‐fit rate‐and‐state friction parameters and their standard deviations from averaging 13 experiments at equivalent conditions. We find evidence of similar velocity‐strengthening behavior with 50% by volume debris‐laden ice slid against till under the same conditions. In contrast, velocity‐weakening and linear time‐dependent healing of ice–till slip is present at temperatures slightly below the melting point, providing an experimentally supported mechanism for subglacial seismicity on soft‐beds. The stability parameter (⁠a−b⁠) decreases with slip velocity, and evolution occurs over large (mm scale) displacements, suggesting that shear heating and melt buildup is responsible for the weakening. These measurements provide insight into subglacial stiffness in which seismicity of this type might be expected. We discuss glaciological circumstances pointing to potential field targets in which to test this frozen seismic asperity hypothesis.

著录项

获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号