VOLCANIC EARTHQUAKES 
109 
The isoseismal lines of intensities 10, 8, 6, 4, and 2 (Mercalli 
scale) are shown in Figure 4, the line of intensity 10 being also 
represented by the 
curve D in Figure 2. 
The meizoseismal area 
(bounded by the iso- 
seismal 8) is a slightly 
sinuous band, running 
from N.NW. to S.SE., 
4 miles long, about 3 
mile wide, and 1% 
square miles in area. 
Within it is a band, in- 
cluding Fondo Mac- 
chia, in which the 
destruction of build- 
ings was complete, this 
band being about 3 
miles long and } mile 
wide. Notwithstand- 
ing the great intensity 
within this band, the 
shock was not felt at 
places 6 miles to the 
west, the area within 
the isoseismal 4 con- 
tained not more than 
about 70 square miles, 
and the whole district 
shaken only about 230 
square miles. The 
mean duration of the 
shock was about 8 
seconds. 
1 
I 
| 
fo} | 
Linguaglossa 
I 
| 
! 
I 
! Piedemonte 
+ Riposto 
© Giarre 
Zafferana © ; 
Fleri 0: 6 j 
Trecastagni’, : i 
° o a, 1 aes 
° . . 7| Acireale 
Viagrande 
Scale of Miles 
{0} 5 10 
Fic. 4.—Map of Fondo Macchia earthquake of 
October 15, 1911. 
During the eighteen years (1893-1911) preceding this earth- 
quake, 27 shocks more or less strong originated within the elliptical 
