———e CU 
s EARTHQUAKES AND GEYSERS 
duced in nature. 
lar lines' are distorted (Fig. 217). 
varies greatly with the 
nature of the rock ; for 
some strata transmit 
the wave readily, and 
others retard it. From 
these and other causes” 
the 
a complex movement. 
Starting no doubt as a 
jar, composed of a few 
shock becomes 
waves, it becomes so 
complex that the earth 
vibrates with them; 
and even after the 
actual violence of the 
shock is past, it seems 
as if the rocks were be- 
ing shaken with great 
force and rapidity. 
Sometimes during an 
1 Called isoseismals, or lines along which the earthquake shock reaches 
t 1 1 t 
MAP XX, 
The larthquake 
a 
The violence also 
305 
134 1 
S138 140 142 
Me a 
lotoam, May 2°89. |__| 
AZZ 
C2 
Za 
WK 
yy) 
Diy 
Zi 
A 
Als 
Japanese earthquake, showing distorted iso- 
seismals and decrease in intensity of shock 
Fie. 
217. 
from epicentrum outwards. 
earthquake there are frequent 
small shocks for days, then the violent jarring and 
the surface at exactly the same time (Fig. 216). 
2 Chiefly the reflection of the waves in passing from one rock to another, 
and the wave interference caused by differences in texture. 
Zane 
——-~-- 
144 146 
\\ iy Y, 
S\\\\ GGZ 
YW 
Z Ly 
The wave passes through some rocks 
more rapidly than through others, and hence the circu- 
6 
