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Characteristics of Alaskan earthquake records at distances of 40° to 70°^*

Abstract

ONE HUNDRED AND TWENTY-FOUR Alaskan and Aleutian earthquakes have been recorded at Fordham in the years 1928-1944. The Galitzin-Wilip three-component seismograph recorded 84 of these well enough to supply a basis for the present study. All epicenters lie at about the same azimuth with respect to Fordham, between 311° and 325°, and at distances of from 40° to 70°; the waves reaching Fordham therefore traveled over much the same continental paths. P was often late in terms of Macelwane's tables; emergences and impulses were almost equal in number, the former predominating slightly; often, an emergence was soon followed by a sharp impulse. S was usually sharp on both horizontals. No evidence of False S was found. Reflected phases were not prominent in the records, PR₁ being recorded on only about 20 per cent of them, SR₁ on about 30 per cent. The surface waves were confused and difficult to identify; only very general conclusions can be drawn about them, the most significant being a dominant period of 13.5 seconds in the coda.

Footnotes

^* A preliminary report of this paper was given at the joint meeting of the Seismology Section of the American Geophysical Union and the Eastern Section of the Seismological Society of America in June, 1944, at Georgetown University, Washington, D.C. Abstracts appeared in Transactions of 1944 of the American Geophysical Union and in Earthquake Notes for March, 1945. Manuscript received for publication August 19, 1946.