The evening times. [volume] (Grand Forks, N.D.) 1906-1914, 1906-05-01

For this reason the vibrations record
ed at Washington undoubtedly were
transmitted directly through the body
OF the earth, passing under the bases
of the mountains.
BY comparing the recorded times
OF the occurrence of the first shock
at San Francisco and of the beginning
of the vibrations at Washington we
can deduce the speed with which the
earthquake wave rushed through the
solid globe. The first shock at San
francisco was at 5:13 a. M, Pacific
time. That would correspond at S:13
a. M, Eastern time. The first vibra-
tons reached Washington at $3.50,
Eastern time. Consequently, the act
ual time elapsed while they were
crossing the continent was IL minutes!
This corresponds to speed of 1761h
miles per minute, or 1852 feet per
second, assuming that the total dis
lance traversed was 5000 miles, and
that the times are accurate. This is
somewhat above the highest recorded
speed of earthquake waves hitherto
known, although they have been found
travelling more than 10000 feet per
second
Vibrations taking still deeper
course through the earth would
emerge in the Atlantic ocean. Very
deep ones might reach the coasts of
Europe and be recorded by seismic
instruments there. They would prob
ably, however, be very weak at that
distance.
In the other direction the shocks
must have been transmitted to the Pa
cific ocean with considerable violence,
and ships at sea may possibly have
noticed them, and they may have
reached Hawaii or even the Eastern
coast OF Asia. They must also have
spread north and south.
In regard to the question of danger
on the Atlantic coast from great
earthquake shock in California;
question that has been raised on ac-
count of the phenomena noticed in
Washin2ton-it should be said that it is
practically impossible that any serious
effect of that kind could be produced.
The most destructive, and possibly the
most powerful earthquake on record
was that of Lisbon in 1855, but while
on that occasion a sea wave was sent
across the Atlantic ocean in nine and
half hours, and more or less severe
shakings were experienced as far away
as the British Islands. the serious
damage was confined to the city of
Lisbon and its immediate neighbour
hood.
This is incomparably the greatest
earthquake that California has ever
known, and in the destruction of life
and property the greatest that ever oc-
Cured in the United States. 1t should
probably be placed in the second class
OF such phenomena, as they were di-
vided by the late Professor Shaler.
The first class comprises all earth
quakes of such intensity that no
masonry can stand against them, and
that the ground is shaken "as in
sieve The second class comprises
earthquakes that shake down all but
the strongest buildings and often leave
long rents in the rocks and crevices
in the ground. The third class of
earthquakes is only strong enough to-
damage weak buildings and bring
down few chimneys.
When. as is the fact, we have evil
dence that shocks can be transmitted
directly through the great S,OO0-mile
ball of the earth it is not difficult to
understand that such shocks may act
like touch upon hair-trigger, set
ting off explosions whose preliminary
conditions have been long before pre-
pairing in consequence of the strains
in the slowly settling and shrinking
crust of rock.
The shrinking needs to be but very
slight, and absolutely invisible as
measured by the decrease in the diam
eter of the globe 4 drop or slip
OF single inch in the underlying rock
would be sufficient TO account for all
the destruction wrought in San Fran
cisco, and, indeed. for much greater
calamity, provided that the part of the
earth's crust affected by the slipping
and shrinking is of considerable en-
tent.