The Black Hills union and western stock review. [volume] (Rapid City, S.D.) 1904-19??, 1906-05-04
beyond the rim of the contain,

ing vessel.
The destructive effect of
earthquake shocks so far as
concerns the work of man de-
pends primarily upon the sud
denness and strength of the
minute vibrations of the trans
mitting rock, the irregularities
ofpropogation and the freedom
of movement of the bodies act
ed upon. Just as a slight quick
tap ola hammer on a table top
may throw glass ball several
inches into the air so a solid
rock mass may transmit its vi
brations of slight amplitude to
a building and overwhelm it.
The disturbing effect Of
earthquakes is oftentimes de-
ceptive. 1t is general only when
artificial structures are influ-
enced that we are compelled to
take note of the results. In
thickly1 settled regions there is
abundant opportunity for dis
asterous phenomena by agita-
tion and often as at San Fran
cisco accidental fires add de-
struction to the previous dis
order. The geological effects
are only occasionally pro-
nounced-open cracks may be
formed in the earths crust, the
flow of springs may be acceler-
ated or retarded, land and
snow slides may be produced,
and rarely important elevations
OF depressions Of land surfaces
may occur.
The areal distribution of
earthquake disturbances is
much the same as that of vol
canoes aud between the two
there is close relationship.
Earthquakes as we'll as active
volcanoes are confined almost
entirely to the vicinity of the
sea-but rarely are there I'M
portant exceptions. Further
than this they occur in particu-
lar prominence in two irregu-
lar belts extending around the
earth approximately at rig hit an
giles to each other, one belt fol-
lows in a general way the shores
of the Pacific, the other lies ap-
proximately parallel with and a
little to the north of the equa-
tor. Where these belts cross
each other, namely, in the Cen
tral-American West Indian re-
gion and in the East Indian
Polinesian region the agitation
is frequent and pronounced.
Much of the land area outlined
by these belts is densely popu-
lated and the i inhabitants in sew
eral Of the countries traversed
plan their dwellings in conform
ity with the known tendencies
of destruction, The islands of
Japan show an average Of three
or four shocks per day and the
japanese have as a consequence
by discriminating observation
and by Improvement Of seismo-
graphs developed the study of
earthquake phenomena to a
marked degree. In California
where for twenty years or more
careful record has been kept Of
the earthquakes there is an av-
erage Of more than thirty shocks
per year. Some Of these have
locally been quite destructive
although so far as the writer is
informed none prior to the
present year have brought
about a money loss Of mora
than a few hundred thousand
dollars. Various educational
institutions and observatories
within the state. are equipped
with seismographic apparatus
and careful note is made of
statements given by responsible
individuals where seismographs
are not provided.
In view Of recent volcanic
and earthquake disturbances at
Vesuvius, Mt. Pelee, Formosa
island and elsewhere the ques-
ton naturally comes: Is there
any relation or connection be-
tween these and the California
disturbance. AS for positive
answer we may never know.
Certainly in the light Of recent
earthquake study this is not an
Iimpossibility. We know that
disturbances Of this character