Abstract

The initial motions of the P and S phases have been tabulated from the original seismograms of sixty earthquakes which recorded at the Florissant station in the years 1927–1938. The epicenters of these earthquakes were within limited areas of the following regions: the Aleutian Islands, the west-central coast of South America, and Central America.

The study indicates that the Florissant seismograms show a preferential direction of motion for both P and S waves in the recordings of certain earthquakes from selected regions. The data compiled on the S phase indicated that a majority of the Aleutian and South American earthquakes recorded a sharp impulsive initial northeast motion at Florissant. The Central American earthquakes studied recorded S phases of somewhat indefinite onset which did not exhibit a preferential motion as they were read.

The results of the application of Neumann's method of S-wave analysis to the Saint Louis seismograms of two selected Aleutian Island earthquakes are presented and a brief discussion of some possible structural implications of the various data is given.

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