Rit (Vísindafélag Íslendinga) - 01.06.1967, Qupperneq 72

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253 fcm long profile was measured by Báth (1960) in west-
ern Iceland and two 100 km long profiles were recently mea-
sured off the west coast. The results which are presented
here are based partly on the above reports and partly on pre-
viously unpublished measurements. A more detailed report
on these latter measurements will be published elsewhere.
Geographical distribution of refraction profiles
Fig. 5 shows the geographical distribution of most of the
shorter refraction profiles. Each number denotes one profile.
Several additional profiles have been measured, mainly in
southem and northwestern Iceland, but these are not shown
here as their results have not yet been evaluated. Báth’s long
profile from Graenavatn on the Reykjanes Peninsula is also
shown as well as the two offshore profiles off the west coast.
The majority of the profiles are unreversed, but in areas
where there is a sufficient number of profiles, errors due to
this are not likely to be important.
General features of tlie results
Fig. 1 shows the crustal structure obtained by Báth (1960)
from the 253 km long profile in westem Iceland, together
with his interpretation. The surface lava layer has later been
found to be more complex than here indicated, usually con-
sisting of 2—3 layers with P-velocities in the range between
about 2.5 km/sec to about 5.5 km/sec. The two deeper lay-
ers with velocities 6.71 km/sec and 7.38 km/sec are inter-
preted as basalts. On the basis of reflected waves Báth inter-
prets a Moho-discontinuity at a depth of 27.8 km, but this
interpretation must be considered somewhat uncertain.
Most of the seismic refraction work has been aimed at
mapping the upper part of the crust to a depth of 5—10 km.
A certain characteristic layering has been found and the seis-
mic velocities which have been observed fall into four or
five groups. Fig. 2 shows a histogram of all presently avail-