Rit (Vísindafélag Íslendinga) - 01.06.1967, Page 85

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Fig. 1. Crustal structure of lcelandL as deduced from surface wave
dispersion. (Tryggvason, 1962)
up to 1000 km from Iceland. He used the conventional me-
thod of interpretation, i.e., theoretical curves were calculated
according to some assumptions about the structure. The theo-
retical curves were then compared to empirical curves, and
the hest fitting curves selected to represent the structure.
After applying this method to sixteen earthquakes recorded
in Reykjavík and Akureyri a crustal structure was deduced
which is shown in Fig. 1. One should, however, bear in
mind that such results are not necessarily unique. In the very
last years the so called higher modes of surface waves have
come into use as a complement to the fundamental modes.
Secondly the use of higher modes gives sometimes a different
solution. Some higher modes are especially useful for upper
mantle studies. Thus the study of higher modes of earth-
quakes near the Mid-Atlantic Ridge is a very interesting
problem.
It can be considered as rather well established that at a
depth of about 15 km under Iceland there is a velocity dis-
continuity, i.e. the velocity of P waves suddenly increases
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