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resulting in a compression score that corresponded to a
rutschblock score.Themedian andrangeofcompres-
sionscoresfor52rutschblockscoresranging from2-7
are plotted in Figure 8.Forrutschblock scores of2,the
two compression scores are in the easy-moderate range.
For rutschblock scores of 4, compression scores are gen-
erally in the moderate range. For rutschblock scores of 5
or 6, compression scores range from moderate to moder-
ate-hard.And forrutschblock scoresof 7,compression
scoresaregenerallyinthehardrange.Exceptforfive
rutschblock scores of 3,median compression scores in-
crease as rutschblock scores increase from2 to 7.Based
on these limited and preliminary data,there appears to
bea correlationbetween rutschblockandcompression
scores.Further field studies are planned.
Although the compression testis considerably faster
than the rutschblock test,it is unlikely to prove to be as
good an indexof slab stability for skiers as therutschblock
whichtestsan area over30timeslargerand loadsthe
area with a skier.
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CORRELATIONWITHSKIER-TRIGGERING
During the winterof 1996,compression tests were done
at 21 skier-tested slopes, eight of which produceddry slab
avalanches.Foreach slope,thecompressiontestswere
done at asitejudged typical ofthe start zone.On some
slopes where skier-testing did not release avalanches, the
compression test found more than one weak layer, thereby
providing more than one skier-tested slab forthe correla-
tion.
The depths of the weak layers for the skier-tested slabs
are plotted against the average number of taps required to
cause failures in theweak layers (Figure 9). There wasonly
one skier-tested slab with an easy compression score (1-7
taps).Most ofthe skier-triggered slabs fall in the easy-to-
moderate (8-12 taps) or moderate (12-17 taps) ranges. The
graph also identifies one slab that was triggered remotely
(17 taps) and one that was triggered from near the bottom
of the slope (30 taps).Although the site chosen forthe
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