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The seismicity of the Arctic

LAMONT GEOLOGICAL OBSERVATORY COLUMBIA UNIVERSITY, PALISADES, NEW YORK

Abstract

All well-recorded earthquakes in the Arctic for the period January 1955 to March 1964 were relocated using a digital computer. The accuracy of the relocated epicenters is about 10 km. Many tectonic features can now be recognized that were not resolvable previously because of the uncertainties in the epicentral locations.

Excluding Alaska, the most seismically active region in the Arctic is found along an extension of the mid-oceanic ridge. South of Iceland the epicenters are located along a single, narrow, linear belt on the crest of the Mid-Atlantic ridge. North of Iceland the seismic belt changes direction abruptly. The seismic pattern indicates that a large east-west fracture zone intersects the mid-oceanic ridge near Jan Mayen. Between northeastern Greenland and northern Siberia, the earthquake belt is remarkably narrow and straight for a distance of more than 20°. Within the Eurasian continent, however, the extension of the mid-oceanic seismic belt is no longer confined to a single, narrow zone. Several epicenters were also found along the crest of the Mid-Labrador Sea ridge.

Nine years of data from 267 earthquakes were used to derive the relationship log N = 6.12-0.91 M, where N is the number of earthquakes larger than magnitude M. The constant b = 0.91 is typical of values obtained in other areas of the world and is the first determination of this constant for the mid-oceanic ridges that is based on a reasonably large sample of events.

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