Seismic data from Colle Gnifetti glacie saddle around borehole KCI, Swiss Alps

Two seismic surveys were carried out on the high-altitude glacier saddle, Colle Gnifetti, Monte Rosa, Italy/Switzerland. Explosive and vibroseismic sources were tested to explore the best way to generate seismic waves to deduce shallow and intermediate properties (<100 m) of firn and ice. The explosive source (SISSY) excites strong surface and diving waves, degrading data quality for processing; no englacial reflections besides the noisy bed reflector are visible. However, the strong diving waves are analyzed to derive the density distribution of the firn pack, yielding results similar to a nearby ice core. The vibrator source (ElViS), used in both P- and SH-wave modes, produces detectable laterally coherent reflections within the firn and ice column. We compare these with ice-core and radar data. The SH-wave data are particularly useful in providing detailed, high-resolution information on firn and ice stratigraphy. Our analyses demonstrate the potential of seismic methods to determine physical properties of firn and ice, particularly density and potentially also crystal-orientation fabric.

本数据集依托于意大利/瑞士边境罗莎峰（Monte Rosa）格里涅蒂冰川鞍部（Colle Gnifetti）开展的两次地震勘探作业。本次研究测试了爆炸震源与振动地震（vibroseismic）震源，旨在探索最优地震波激发方案，以反演粒雪（firn）与冰体浅部及中层（深度<100 m）的物理属性。
爆炸震源（SISSY）会激发强烈的面波与下行波，对数据处理质量造成负面影响；除了噪声严重的基底反射信号外，未观测到任何冰内反射波。不过，通过对强下行波的分析可反演粒雪层的密度分布，所得结果与附近冰芯的测量结果高度吻合。
振动震源（ElViS）可兼容纵波（P-wave）与SH波两种工作模式，能够在粒雪与冰体柱中激发可被有效检测的横向相干反射信号。我们将此类反射信号与冰芯及雷达探测数据开展了对比分析。其中SH波数据可提供粒雪与冰体层序（stratigraphy）的高分辨率精细信息，应用价值显著。
本次研究证实了地震勘探方法在测定粒雪与冰体物理属性方面的应用潜力，尤其是密度参数，同时也有望用于反演晶体定向组构（crystal-orientation fabric）。