S n o w

C o v e r

S t a b i l i t y,

A v a l a n c h e

I n i t ia t i o n

a n d

F o r e c a s t i n g

compression tests on the bottom-triggered slope appeared
typical of the start zone, the high score (30 taps) suggests
that the slab was more stable at the top of the slope than at
the trigger point 80 mdown-slope.
Using the six ranges of compression scores (very easy,
easy, easy-moderate, moderate, moderate-hardand hard),
Figure 10 shows the frequency of skier triggeringdecreas-
ingfrom50%(2of4skier-testedslabs)to9%(1of11)
with increasing compression scores.Based on these pre-

CompressionScoresforAdjacentRutshbl ockTests

Purcells,Cariboos,MonasheesWinter1995-96

liminarydata,the compression testshowspromise asa
index of slab stability for skiers. However, because of natu-
ral snowpack variability,no stability test done atone or
two sites on a start zone can provide a definitive index of
stability forthe slope (Jamieson 1995,p.185-194).
Nevertheless, since the compression-tested slabs range
upto1 minthickness(Figure 9),thecompression test
appears tohave the potentialtotestslabsovermuch of
the range forwhich skier-triggering is common.

Average

CompressionScore(No.ofTaps)

Figure 8 Compression scores adjacent to rutschblock tests

Figure 9 Depths of weak layers and compression scor es for skier-
tested slabs

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