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Amplitudes of horizontally refracted Love waves

S. GREGERSEN^* and L. E. ALSOP

LAMONT-DOHERTY GEOLOGICAL OBSERVATORY OF COLUMBIA UNIVERSITY, PALISADES, NEW YORK 10964
IBM TH.J. WATSON RESEARCH CENTER YORKTOWN HEIGHTS, NEW YORK 10598

Abstract

Love-wave transmission and reflection are studied numerically for a vertical interface between two layered models. By a new method of approximation, the transmission and reflection coefficients can be computed for propagation directions differing from normal incidence. We consider the Love mode as a superposition of propagating plane SH waves in a surface layer and an inhomogeneous plane SH wave falling off with depth in the half-space below. The method is based on satisfying all boundary conditions on the vertical interface and computing the coupling between the interface stress displacement pattern and the transmitted/reflected Love modes. The computations are done rapidly on a small computer.

The transmission coefficients change rapidly with period. For propagation from ocean to continent, they increase with decreasing periods in the interval 60 to 20 sec. The opposite trend is found for propagation from continent to ocean. The amplitude transmission coefficient curves show almost no dependence on the angle of incidence except for large angles. The fine structure of the curves is similar to that for plane SV waves incident on an interface between two homogeneous elastic media. Love-wave amplitude observations at OBS on the ocean bottom northwest of San Francisco and at BKS in Berkeley also show these trends as a function of period and of angle of incidence.

Footnotes

^* Present address: Geodetic Institute, Gamlehave Alle 22, Dk 2920 Charlottenlund, Denmark.

Present address: Geophysical Institute, University of Karlsruhe, Hertzstrasse 16, 75 Karlsruhe, Federal Republic of Germany.