Icequake streaks linked to potential mega-scale glacial lineations beneath an Antarctic ice stream
Icequake streaks linked to potential mega-scale glacial lineations beneath an Antarctic ice stream
复制标题
冰震条纹与南极冰流下方潜在的巨型冰川线条有关
作者：
C. G. Barcheck;S. Schwartz;S. Tulaczyk
从冰流基地辐射出来的冰震提供了对亚千米尺度基底非均质性的观察。我们在南极洲西部的Whillans冰平原（WIP）上安装了一个宽约3公里的地震传感器网络，在该网络下探测到基底冰震，并使用s波反投影分别在2014年1月和2015年1月的14天和21天内探测和定位了数千次基底冰震。我们在WIP下方发现了基底冰震的流动平行条纹，我们推测这与冰透雷达显示的超大尺度冰川线（MSGLs）的存在有关，其中至少有一条条纹起源于与MSGLs相邻的局部槽。基底地震活动性的模式可以由基底孔隙压力、基底材料摩擦特性或两者的系统空间变化引起。我们将这些流动平行的冰震条纹解释为由于流线型冰流床存在的摩擦非均质床物质：床状脊对应于地震，高孔隙度变形的土，一些槽对应于较深的地震物质的短暂暴露，如淤积土或较老的沉积物或岩石。我们的结果与MSGL的形成是一致的，要么是通过槽内的侵蚀暴露出更深的发震物质，要么是在床型高点沉积地震高孔隙度。我们的研究结果还表明，不断变化的冰下地貌可以通过重组具有不同力学性质的基底物质的空间分布来影响基底牵引力。
Icequakes radiating from an ice-stream base provide insights into otherwise difficult to observe sub-kilometer-scale basal heterogeneity. We detect basal icequakes beneath an ∼3-km-wide seismic sensor network installed on the Whillans Ice Plain (WIP) in West Antarctica, and we use S-wave back-projection to detect and locate thousands of basal icequakes occurring over 14 and 21 days in January 2014 and 2015, respectively. We find flow-parallel streaks of basal icequakes beneath the WIP, which we conjecture are related to the presence of mega-scale glacial lineations (MSGLs) indicated by ice-penetrating radar, with at least one streak originating in a local trough adjacent to a MSGL. Patterned basal seismicity can be caused by systematic spatial variation in basal pore pressure, bed-material frictional properties, or both. We interpret these flow-parallel icequake streaks as being due to frictionally heterogeneous bed materials in the presence of a streamlined ice-stream bed: bedform ridges correspond to aseismic, high-porosity deforming till, and some troughs to ephemeral exposures of deeper, seismogenic material such as lodged till or older sediments or rocks. Our results are consistent with MSGL formation by either erosion in troughs to expose deeper seismogenic material, or deposition of aseismic high-porosity till in bedform highs. Our results also suggest that evolving subglacial geomorphology can impact basal traction by reorganizing the spatial distribution of basal materials with varying mechanical properties.
影响因子：
3.3
作者：
Stokes C
通讯作者：
Stokes C
影响因子：
5.2
作者：
Bindschadler, R.;Choi, H.;Young, N.
通讯作者：
Young, N.