Jökull - 01.12.1980, Page 52

(r = 0.65), and between length and maximum
throw (r=0,64). This means that only about
40% of the maximum dilation and maximum
throw can be accounted for by the length. The
length is therefore not a very “good” predictor
of either parameter, although they are
statistically related. There is no correlation
between length and orientation (r= — 0.05),
and the orientation shows, practically
speaking, no correlation to the other
parameters. On testing the nonlinear
correlation between length and maximum
dilation, which has the best linear correlation,
I found that it is no better than the linear one.
Width offractures
The average width, in the 1076 points of
measurements, is 0.6 m (Table 1, see also
Table 2). The width and the throw of each
fracture was measured at intervals of 107 m.
There is a tendency for increasing width with
increasing length, but the correlation is not
strong — as discussed before. On the average,
the maximum width of all the fractures is 1 m,
but the maximum width on a single fracture is
7.5 m — two points on Hrafnagjá (Fig. 8).
There is a reasonable correlation between
maximum width and maximum vertical dis-
placement (r = 0.62), but the general corre-
lation between width and throw is small (Fig.
9). Regression analysis for fracture number 36
(Fig. 9) gave r = 0.17.
TABLE3.
Total dilation in 11 profiles. The profiles
are shown in Fig. 3 (see also Fig. 4a,b). —
Heildargliðnun í 11 sniðum. Sniðin eru sýnd á Mynd
3 (sjá einnig Mynd 4a,b).
Profile Dilation
1 1 m
2 5 -
3 9 -
4 15 -
5 9 -
6 15 —
7 3 -
8 4 -
9 3 -
10 0 -
11 0 -
In each of the eleven profiles (Fig. 3 and Fig.
4a,b) I calculated the dilation. The result is
given in Table 3. In these calculations only
open fractures have been used; no account has
been taken of closed faults, simply because
they are all verticál or nearly so. Although
there are many minor fractures (Fig. 10), not
seen on the air photos and therefore not in-
cluded in the calculations, these are usually
only of local importance and do not con-
Fig. 8. Fracture number 67,
Hrafnagjá. Width is up to 7.5 m,
and visible depth is over 10 m.
The fracture walls are nearly
vertical. — Mynd 8. Sprunga númer
67, Hrafnagjá. Víddin er upp í 7.5
m, og sýmlegt dýpi er yfir 10 m.
Sprunguveggirnir eru sem nœst lóð-
réttir.
50 JÖKULL 30. ÁR