refraction results discussed above. The average
velocities over the upper 30 m were 1090 m s1 for
the P waves and 250 m s1 for the two S waves.
120
3.3. Environmental characterization
A number of meteorological parameters were
recorded continuously at the site of the seismic
80
and acoustic experiments. A Campbell Scientific
Inc. (CSI) Model 21X Micrologger was used to
collect the data (Fig. 13), which were recorded on
a cassette magnetic tape and written on a paper
40
tape. CSI Model 107 thermistors recorded the tem-
peratures in the ground, in the snow, and at heights
of 0.01, 0.1, 0.3, 1, and 1.4 m above the snow. These
readings have an accuracy of 0.2C. A CSI Model
207 sensor provided the temperature and relative
0
0
10
20
30
humidity at a height of 2 m. The wind speed and
Slant Range (m)
direction at a height of 3 m was recorded by Met
One Model 014A and 024A sensors with an accu-
Figure 12. Radial shear (S) wave downhole travel time
racy of 2% and 5%, and a YSI Model 2014 barom-
analysis. A velocity of 180 m s1 down to 16 m, with 380
m s1 below that, is indicated by the least-squares line
eter provided the barometric pressure to within 1
mb. Readings from the 12 sensors were taken
fit.
every minute, and the average and standard
Figure 13. The instrumentation used to record meteorological pa-
rameters. The Campbell micrologger is housed in the box at the center
of the tripod. At the top are the wind speed and direction sensors. The
radiation shield contains a thermistor and the relative humidity
sensor. Additional thermistors and a barometer are mounted on the
wooden post. A leadacid battery below the tripod provided the
power.
13
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