Earthquake Echoes

Abstract

AN earthquake disturbance, as recorded at a station far removed from its origin, shows that the main movement has two attendants—one which precedes, and the other which follows. The first of these by its characteristics indicates what is to follow, whilst the latter in a very much more pronounced manner repeats at definite intervals, but with decreasing intensity, the prominent features of what has passed. Inasmuch as these latter rhythmical but decreasing impulses of the dying earthquake are more likely to result from reflection than from interference, I have provisionally called them Echoes. Although I see an explanation for the orderly arrangement and features of the precursory vibrations, it is sufficient if I confine my remarks in this note to the reverberations which apparently succeed an earthquake.