S-P conversion at the base of the crust

Abstract

Tlie long-period seismic records at Umeà (Sweden) of
an intermediate-depth earthquake in Burma 011 27 February, 1964, exhibit
an exceptionally clear case of 8-P conversion at the Mohorovicié discontinuity.
The records are examined from various points of view (arrival
times, amplitude ratios, particle motions) and comparisons are made for
each test between observations and theory. General aspects of mode conversions
at the base of the crust are discussed, both their importance and
why they are so seldom observed.