Rit (Vísindafélag Íslendinga) - 01.06.1971, Page 68

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GUÐMUNDUR PÁLMASON
depth to layer 3 on the southernmost part of the profile is consequent-
ly found to he 3.7 km. To the north the depth appears to increase at
first, reaching about 5.0 km near the farm Grund, and then decreases
somewhat, reaching about 4.7 km near Akureyri. The agreement be-
tween the depths computed for the end points of profiles F and G is
very good, as it should be since these stations are fairly close to
each other.
In Fnjóskadalur just east of Eyjafjördm- profile 9 runs southward
from a shot point near the farm Draflastadir. The P3-wave delay time
is about 0.50 sec, and no structural variations are indicated in a north-
south direction. The part of the profile on which the P3-wave is ob-
served, is only about 7 km, so that structural changes may exist out-
side this part. The depth indicated to layer 3 is about 3.5 km, which
differs by more than 1 km from the value obtained in Eyjafjördur on
profile F. A structural change between Fnjóskadalur and Eyjafjördm
is thus indicated in the opposite direction to that which was observed
across the Skagafjördur valley.
East of Fnjóskadalur, in Ljósavatnsskard, a reversed profile (10
and lOa) was measured, with shot points in lake Ljósavatn and near
the western end of the pass. Only the eastward trending profile was
sufficiently long to record the P3-wave as a first arrival. This profile
crosses the Bárdardalur fault without showing any signs of struc-
tural changes associated with it. The total delay time of the P3-wave
is about 1.0 sec (cf. Fig. 25). If the shot point delay time is the same
as was found on the Fnjóskadalur profile, about 0.50 sec, it follows
that the delay time at the eastern end of the profile is also about 0.50
sec. No anomaly in the P3-wave delay time is thus observed across
the Bárdardalur line.
On the highland south of Skagafjördur and Eyjafjördur four pro-
files have been measured. One is profile D of Tryggvason and Báth
(1961), which is located between Langjökull and Hofsjökull. The
other three, 6, 7 and 8, are on the highland south of Eyjafjördur be-
tween Hofsjökull and Vatnajökull. The delay times of the P3-wave
on these profiles are higher (cf. Fig. 20) than on the lower lying pro-
files, the difference being due mainly to the higher elevations.
On the Kjölur profile (profile D) the delay time is increasing
slightly in the direction of the profile to the north. A delay time of
about 0.65 sec is indicated near the shot point, increasing to about
0.75 sec at the northern end. Tryggvason and Báth (1961) assumed
that a layer with P-wave velocity of 5.6 km/sec was present on this