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  • Hofstede, Coen  (3)
  • Polom, Ulrich  (3)
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  • 1
    Online Resource
    Online Resource
    Joint interpretation of explosive and vibroseismic surveys on cold firn for the investigation of ice properties
    International Glaciological Society ; 2013
    In:  Annals of Glaciology Vol. 54, No. 64 ( 2013), p. 201-210
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 54, No. 64 ( 2013), p. 201-210
    Abstract: 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.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/2013AoG64A200
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2013
    detail.hit.zdb_id: 2122400-6
    SSG: 14
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Influence of ice crystal anisotropy on seismic velocity analysis
    International Glaciological Society ; 2014
    In:  Annals of Glaciology Vol. 55, No. 67 ( 2014), p. 97-106
    Details
    In: Annals of Glaciology, International Glaciological Society, Vol. 55, No. 67 ( 2014), p. 97-106
    Abstract: In 2010 a reflection seismic survey was carried out on the Alpine glacier Colle Gnifetti. The processed and depth-converted data could be compared to a nearby ice core, drilled almost to the bed. Comparisons showed that the depth of the P-wave bed reflection was too shallow, while the depth of the SH-wave bed reflection fitted the ice-core length well. We are now able to explain the major part of these differences using the existing crystal orientations of the ice at Colle Gnifetti. We calculate anisotropic velocities for P- and SH-waves that are usually picked for stacking and compare them with zero-offset velocities needed for the depth conversion. Here we take the firn pack at Colle Gnifetti into account for P- and S-wave analysis. To incorporate the S-wave analysis we first derive a new equation for the relationship between density and S-wave velocity from diving waves. We show that anisotropic fabrics observed at Colle Gnifetti introduce a difference of only 1% between stacking and depth-conversion velocities for the SH-wave, but 7% for the P-wave. We suggest that this difference in stacking and depth-conversion velocity for the P-wave can be used to derive information about the existing anisotropy by combining our seismic data with, for example, radar data.
    Type of Medium: Online Resource
    ISSN: 0260-3055 , 1727-5644
    URL: Article
    DOI: 10.3189/2014AoG67A002
    Language: English
    Publisher: International Glaciological Society
    Publication Date: 2014
    detail.hit.zdb_id: 2122400-6
    SSG: 14
    Location Call Number Limitation Availability
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  • 3
    Online Resource
    Online Resource
    First glacier‐vibroseismic experiment ‐ results from cold firn of Colle Gnifetti
    Wiley ; 2014
    In:  Near Surface Geophysics Vol. 12, No. 4 ( 2014-08), p. 493-504
    Details
    In: Near Surface Geophysics, Wiley, Vol. 12, No. 4 ( 2014-08), p. 493-504
    Abstract: In the summer of 2010, a small shallow reflection seismic experiment was carried out on the firn covered cold glacier of Colle Gnifetti, Monte Rosa group, Swiss/Italian Alps. At this site, the physical properties of ice are comparable to polar conditions, which is why this site is often used for methodological tests. The experiment at 4500 m elevation was designed to explore the scope of shallow vibroseis for seismic targets within and below the glacier. A small ELVIS vibrator system was used to generate shear waves and compression waves for SH‐ and P‐wave receiver setups of two profiles. The resulting sections clearly show a boundary from ice to rock around 60 m and deeper structures below the glacier. The deepest features are estimated to be 150 m for the SH‐waves and 220 m for the P‐waves. Reflections could be detected also within the ice overburden, which are preliminarily interpreted as a change of density in the upper 30 m and possibly crystal orientation fabric in the ice column. Furthermore, elastic parameters could be derived from seismic velocities, due to clear basement reflections. The results of this unique experiment enable new insights into the internal structure of ice masses and open a promising new investigation method for sub‐ice structures and properties, such as basal sediments.
    Type of Medium: Online Resource
    ISSN: 1569-4445 , 1873-0604
    URL: Article
    DOI: 10.3997/1873-0604.2013059
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 2247665-9
    SSG: 16,13
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