Rit (Vísindafélag Íslendinga) - 01.06.1967, Blaðsíða 92

88
A zone with small earthquakes mainly occurs farther east
with nearly north—south direction. The distribution of the
earthquakes could fit with a general east—west tension in
the region. Large earthquakes originate from east-west shear
zones where large horizontal shear stresses can develop.
Small earthquakes are frequent in the north-south zones
where uniform tension is dominating. This explanation is,
of course, very hypothetical, but it is an idea which requires
a thorough investigation. It is necessary to locate carefully
the epicentre and hypocentre of the earthquakes in the north
-south earthquake zone, by increasing the number of good
permanent stations by one or two so these would become
four or five, and by portable seismographs operated at diffe-
rent times in different regions. This is an extremely urgent
investigation and cannot possibly be carried out in other
localities on the Mid-Atlantic Ridge than Iceland, at least,
not in the near future.
REFERENCES
Ewing, J. and M. Ewing, 1959: Seismic-refraction measurements in the
Atlantic Ocean basins, in the Mediterranean Sea, on the Mid-Atlan-
tic Ridge, and in the Norvegian Sea. Bull. Geol. Soc. Am., 70: 291
-318.
Heiskanen, W. A. and F. A. Vening Meinesz, 1958: The earth and its gra-
vity field. McGraw-Hill, New York, N.Y., 470 pp.
Scheidegger, A. E., 1966: Tectonics of the Arctic seismic belt in the light
of fault-plane solutions of earthquakes. Bull. Seismol. Soc. Am., 56:
241-249.
Stauder, W. and G. A. Bollinger, 1964: The S-wave project for focal me-
chanism studies, earthquakes of 1962. Bull. Seismol. Soc. Am, 54:
2199-2208.
Stauder, W. and G. A. Bollinger, 1966: The S-wave project for focal me-
chanism studies, earthquakes of 1963. Bull. Seismol. Soc. Am., 56:
1363-1371.
Stefánsson, R., 1966: Methods of focal mechanism studies with application
on two Atlantic earthquakes. Tectonophysics, 3: 210—243.
Sykes, L. R., 1965: The seismicity of the Arctic. Bull. Seismol. Soc. Am.,
55: 501-518.