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<abstract>
<title>Ultra high-resolution seismic imaging of permafrost, Devon 
Island, Nunavut</title>
<author>Carlos E. Nieto and Robert R. Stewart</author>
<p>In July-August, 2002, several shallow multicomponent seismic surveys
and ground-penetrating radar traverses were conducted near the NASA
Haughton-Mars Project camp on Devon Island, Nunavut. Geophones and
hammer impacts in three different orientations (vertical, horizontal
inline, and horizontal transverse) with different acquisition
parameters were acquired successfully. Two different locations were
selected to conduct seismic surveying, the Von Braun Valley and the
Gemini Hills. The analysis of the ultra-high resolution seismic lines
allowed the characterization of the saturated silt layer (top layer).</p>
<p>A compressional velocity of 260 m/s and a shear velocity of 168 m/s
were obtained from the first break arrival times. We observe that the
direct compressional wave changes its polarity with offset sign and
with hammer impact orientation. The direct shear wave does not change
polarity with the offset sign but it does with the hammer impact
orientation. A more complex situation occurs with the head wave
arrival. An estimated velocity of 3050 m/s was obtained from first
break arrival times for a pure compressional head wave. Its polarity
remains unchanged with offset. Variation of the velocity suggests
layering in or over the permafrost, and lateral changes. What appears
to be shear wave refraction was identified on the horizontal
elements. An average velocity of 2250 m/s was obtained from first
break arrival times. It was found that the polarity of this event
changes with offset sign.
</p>
</abstract>
