OBSERVATIONS AND THEORY OF MICROSEISMS 1305 
gation of the microseismic waves in the ground to the energy of these waves is transferred to the coast; f de- 
point of observation. pends on the steepness of the coast, the loss of energy 
Energy Transmitted from Surf. The energy trans- due to friction in the water approaching the coast, and 
mitted from surf to the coast [14] depends on the the wind. The kinetic energy H* (per second) of ocean 
QO 5 10 I5 20 25 30 35 40 10 15 20 25 30 35 40 
VY 
730 , /720 
' 735 ‘ 725uL7 
\ 
W Lg 0 E Lg ie 20 W Lg 0 Elg 10 20 
(b) (d) 
_Fia.2.—Relative amplitudes of microseisms (in per cent of the individual average amplitudes for each station for the same days 
with winter microseisms) and corresponding weather maps: (a) and (b) on Feb. 1, 1914; (c) and (d) on March 26, 1914. State of 
swell indicated by Roman numerals (on a scale from 0 to IX). (Afler Gutenberg.) 
kinetic energy of the waves, the type and slope of the waves (period 7’, length L, velocity V, and height H 
coast, the force of the wind, and its direction relative is given approximately by 
to the shore. The greatest energy will be transferred to : ‘ 
the coast when a strong wind drives high ocean waves Bes gLH” _ gVil (1) 
against a steep, rocky shore. Only a fraction f of the 167 Gi 
