Weekly independent. [volume] (Elko, Nev.) 1887-1914, 1909-03-19
The Phenomena Of Earthquakes Described


The phenomena of earthquakes are
interestingly described In recent pub.
ication Of the photographic office, ut
washington, ID. c., in which the general
classes OF seismic waves are defined.
and the manner of escape from danger
pointed out, In part it says:
| "Great multitudes of people live in
cities by the sea and are subjected to
the dangers arising from seismic SEA
waves, and yet, if place of refuge ex.
lists. they usually have ample time to
escape; and even the ships in the harbor
Will generally bc safe if they promptly
put to sea on the first sign, after the
withdrawal of the water. which ALWAYS
indicates that the sea bottom has sunk.
Thus, by the study of the laws of the
physical world and the diffusion of the
resulting useful knowledge, great
measure Of safety may he secured from
some of the most dreadful forces in
nature, and in the course of time the
Interests Of civilization may be enormo.
usly conserved.
There are two general classes of
seismic scL waves. The first is due to
the sinking of the sea bottom, and is
characterized by withdrawal of the
water after the earthquake, to he
followed later by the return of u great
wave; and the second is due to the up.
lift of the bottom, and is characterized
by the sudden rise of the sea without
any previous withdrawal from the
shore. Most of the historical inunda-
tions of the sea have been due to waves
Of the first class. The phenomena
usually noted are: First, an earth
quake: second, after short interval, the
sea is noticed to he draining away, lay
ing bare the bottom where il is or
dinarily deep enough for ship to anchor;
third, after an interval of an hour or
50, the sea is seen to be returning rs a
mighty wave, washing everything be.
fore it, and thus carrying ships shore
ward and stranding them; fourth, hay
ing once swept the shore, the sea again
withdraws and lays bare the harbor as
before, and after about the same inter-
val again returns rs Il second great
wave. This periodic movement of the
sea may bc kept up for quito while,
and sometimes quiet is not restored for
Il day or two.
Seismic sea waves of the second
class are produced by tho uplift of the
Yea bottom into ridges or submarine
plateaus and islands. In such cases the
water raises suddenly without previ-
ously Withdrawing from the shore.
"Thc lesson to be impressed upon
mariners in the light of these expert
ences is that the chances of safety to
shipping are much increased by pro-
cecding to sea, if practicable immedi.
atcly after the occurrence of an earth
quake; and this especially to bc en-.
joined If the water of the harbOr is
found to bc draining away after the
shocks Of earthquake have been felt.
In the open ocean seismic sea waves are
not generally dangerous to vessels, be.
cause their very great length and
moderate height gives them n gentle
slope and their period is very much
longer than that Of ordinary sea waves.
by study of the charts of deep
sea soundings throughout the world. II
can bc told quito closely what the
expected state of seismic activity of any
given region should he, for wherever
there are very deep oceanic troughs
situated adjacent to mountainous ridges,
eliminating either below or above the
surface of the ocean. disturbances of the
crust Of the earth nre likely to bo
prevalent. In these regions tho forces
of nature are, in fact. generally en-
gagged In building up tho ridges by
forcing under them material pushed
from beneath the under mined floor of
the adjacent lCCDoning trough"