Long-Period Waves and Free Oscillations of the Earth

Abstract

Studies of long-period waves culminating in the experimental verification of the earth's free oscillations may be counted among the major advances in solid earth geophysics during the IGY and post-IGY period. Not only are the developments in this field elegant from the standpoints of instrumental design, numerical analysis, and wave theory, but they have also yielded significant new information concerning the earth's interior and the mechanism of earthquakes. In this paper the recent history of the field is reviewed, the analytical methods are described, and the current status is assessed - all from the point of view of the nonspecialist. The rapid progress in this field over the past decade stems from a fortuitous combination of circumstances: the development of instruments sensitive to long-period earth movements and the disposition of these instruments around the world under IGY auspices; the availability of electronic digital computers with concomitant progress in techniques of interpretation of experimental results, particularly through methods of general numerical spectral analysis; advances in the theory of wave propagation in a heterogeneous, spherical earth.

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