Subglacial Bed Properties from Normal-Incidence Seismic Reflection Data
Subglacial Bed Properties from Normal-Incidence Seismic Reflection Data
复制标题
来自正入射地震反射数据的冰下床特性
DOI：
--
复制
发表时间：
2007
期刊：
影响因子：
--
通讯作者：
A. Smith
中科院分区：
文献类型：
--
作者：
A. Smith
总结了最近正入射地震反射技术在冰下条件研究中的应用。该技术的一些重要方面进行了讨论，包括关键的采集参数和特定的优点和缺点。采用这种技术而不是其他地震方法的主要原因是数据采集更简单，需要的资源更少。该技术目前的局限性包括无法确定冰下地震速度，冰的衰减系数的不确定性，以及源重复性的假设。在冰床界面处的反射系数是从一次反射和多次反射之间的能量减少来计算的。由此，推导出床层的声阻抗，并用于解释床层物质。在快速流动的冰下，渗透变形的沉积物与沉积物沉积床区分开来，使用孔隙度作为沉积物膨胀的代表。冰下水和永久冻土也被解释。来自多个地点的数据可用于建立一个完整冰川基本条件的模型。在南极洲西部的冰流站点的结果显示，冰如何遇到或多或少的约束流动，从不同的基础条件。应用在北极的冰川，表明其最近的激增终止时，水通过不连续的永久冻土下的冰逃脱。进一步的冰川学问题，可以解决使用该技术提出。
Recent applications of the normal-incidence seismic reflection technique to studying subglacial conditions are summarized. Some of the important aspects of the technique are discussed, including critical acquisition parameters and particular strengths and weaknesses. The main reason for deploying this technique, rather than other seismic methods, is that data acquisition is simpler and requires fewer resources. Current limitations of the technique include the inability to determine subglacial seismic velocities, uncertainty in the attenuation coefficient for ice, and assumptions of source repeatability. The reflection coefficient at the ice-bed interface is calculated from the energy reduction between primary and multiple reflections. From this, the acoustic impedance of the bed is derived and used to interpret the bed material. Beneath fast-flowing ice, dilatant, deforming sediment has been distinguished from a lodged sediment bed, using porosity as a proxy for sediment dilation. Subglacial water and permafrost have also been interpreted. Data from a number of locations can be used to develop a model of the basal conditions of a complete glacier. Results from sites on ice streams in West Antarctica show how the ice encounters a greater or lesser restraint to flow, from different basal conditions. Application to a glacier in the Arctic, suggests its most recent surge terminated when water escaped through discontinuous permafrost beneath the ice. Further glaciological questions that could be addressed using the technique are proposed.