Evening star., 1923-09-16
BY JAMES A. BUCHANAN.

for many years-in fact for hundreds
of years-the general public has for
gotten for the moment the cause of
these severe disturbances. The great
masses of the people have given the
matter no thought at all.
Many of the ancients made refer
ences to earthquakes, but their con-
ceptions of the causes were fanciful
IND Irrational.
Unsatisfactory attempts were made
by Joseph Priestly and other scien-
lists In the eighteenth century to con-
meet earthquakes with electric phe-
character was established. One may
say that Investigations of seismic pbe-
nomena began in the middle of the
nineteenth century and have been
continued
Investigators have agreed that
earthquakes are caused by the slip
ping of the earth along certain lines.
and this movement is at points known
as faults" Thus. the great earth
quake of October, 1891. in Japan,
known as the Mino-Owari earth
quake, was connected with the for
nation or development of a fault,
which. according TO Prof. B. Koto.
was traced on the surface for a dis
tance of nearly fifty miles and pre-
sented in places a scarp with a YER
tical throw of as much as twenty feet,
while probably the maximum dis
placement underground was very
much greater.
The recent shock was. according to
advices received from the Imperial
University at Toxic. centered in the
sea. a distance of more than sixty
miles from the stricken city, and Prof.
A. Lawson of the University of Cali
fornia states that many of the quakes
that have occurred in the Pacific
ocean area have been caused by the
sinking of the seas floor and that in
places great amounts of rocks have
slipped vertically, or nearly so.
In this same connection Lawson
says that there is little danger of a
| city of any size being engulfed, ow-
ing TO the fact that there is not suf-
ficient room in the region of the fault
for the earth is too compact.
In commenting upon the tidal waves
that almost always follow a shake,
he says that these are caused by the
fact that when the ocean floor sinks
great volumes of water rush in.
The largest vertical displacement
of which there is any record was at
Yakatat, Alaska. where, in 1899. the
fall was forty-seven feet.
=
| CONTRARY to the general belief.
" earthquakes may be Of different
forms. For instance. they may be
undulatcry. that is. along the ground;
they may be vertical. or even rotary.
Many have asked during the past
few days about the frequency of these
disturbances. If we pick out the well
marked earthquake districts of the
world and give to each of them a
seismicity or earthquake frequency
per unit area one-third of that in
Japan, the conclusion arrived at is
that considerable areas of our planet
are. on the average, shaken every half
hour. The great majority of these are
not preceptible, although we find that
from time to time shakes will oc-
cur that are not noticed on land, but
can readily be detected if they oc-
cur near a body of water. There, if
one looks closely. he will note a sue
cession of ripples, on the surface of
the lake or pond. Some scientists say
that the actual range of horizontal
motion of the ground is less than
e-tenth of an inch usually. In Jap
an however. nine inches or even one
foot movement visible to the naked
eye has been recorded.
1t is reported that the recent quake
in the land of Nippon was about sixty
miles distant, and looking up the
quake that occurred at Charleston,
S. c., in 1886, we find that it's focal
center was twelve miles underground.
This conclusion must be regarded as
only approximating the depth, how
ever. 1t is remembered that few
days previous to the shock, quakes
were felt at Summerville, town
about twenty miles distant from
Charleston. The shock at the latter
place was of such severity that in a
little more than a minute nearly every
building in the city was more or less
damaged and many lives were lost.
The San Francisco earthquake was
plainly due to a fault which can be
traced more than 100 miles. Move
ment all along this line was disclosed
by later Investigations. The worst
damage occurred on alluvial soil or
made ground. The great damage that
was done to the city was, of course, the
result of the fire that swept the area,
and once this fire had gained headway,
there was only one way to arrest its
progress, and that was by dynamiting
great areas, so that the flames would
have nothing to feed upon.
The great Neapolitan earthquake in
1887 resulted in the deaths of 12.300
persons. The disaster known as the
great Indian earthquake, sometimes
termed the Assam earthquake, since 1t
was in that province that the effects
were most severe, caused shocks to be
felt over a large part Of India and. in
deed, far beyond its boundaries, For
tunately, the area that suffered greatest
disturbance was a wild country. al
though some towns were in the affected
zone. For instance, at Shillong the
stonework of bridges, churches and
other buildings was levelled to the
ground. The epicentral tract was of
great size, having an estimated area of
5000 square miles.
1t is supposed that this quake was
connected with movement of SUBJ
terranean rock masses Of enormous
magnitude along what geologists call a