The New York herald., 1922-12-03

the earth. often called the crust. seems
rigid and brittle but Is really elastic
Any forcs which Jars the earth pro-
duces vibrations or tfemors: and when
these become acutely perceptifie to hu-
manity they are classed as earthquakes.
These shocks originate at considerable
below tho surface Of the earth
ana when they reach the surface they
spread out much like the circular waves
seen when . stone II thrown into still
water.
Near the eenter Of the shock they
seem almost like hard bloys; at dis
tancs they become trembiings which
gradualiy disappear. Tho explosion Of
heavy blasts produces shocks which dif'
fer from natures earthquakes in energy
only. The blowing up Of Hell Gate rock
was felt forty miles away. Tho mu-
ndtions explosion which shattered the
windows Of lower Manhattan during the
war stopped the chronograph clocks In
the weather bureau laboratory at Mount
Vernon. As . matter Of fact. artificial
resulting from mine explo-
sions have been used In Europe. Tor the
study Of earthquake phenomena |; in tho
future It is likely that they will be ex-
employed for that purpose.
Earthquake vibrations travel VERY
rapidly. A they traverse the. rock
layer they progress with q velocity es-
timated at from 100 to 15o miles min
ute. The earth waves created In the
ocean move more slowly. Their velocity
varies from six to ten miles minute.
OF the various causes Of earthquakes
two have been pretty thoroughly inves-
tigated. In volcanic regions explosive
Of aubterranean steam or
other gases cause violent and destruc-
tive shocks. As q rule shocks OF this
kind arc almost momentary. each last
ing from q few seconds to a minute.
Sometimes they precede q volcanic erup-
ton; sometimes q volcanic .outburst
produces all the phenomena OF m earth
quake. Tho eruption Of Krakatoa. .
volcano near Java, was coincident with
4 severe earthquake the volcanic ex-
plosion itself caused the earth tremors.
But q fundamental cause OF earth
Quaies Is the gradual adjustment OF
the rock envelope around shrinking
The great mountain systems
with their wrinkles. folds and block
ranges are the result of such ADJUST
ment. The rock layer folds itself about
the shrinking interior not by bending
but by innumerable fractures or breaks.
The breaks and eiiearings Of the vari-
Gus strata which form the crust are the
faults Of the geoiogist. Some Of the
faults thus produced are hundreds Of
miles in length; others are almost In
significant In extent. One may see
many Of the minor faults along the rock
cuts Of the New York, westchester and
Boston Railway. The parallel seams in
the granite rock arc faults; and where
the shearing occurs the rock has been
thrust upward, or downward, or side
wise. These displacements are slight
and the, shock duo to the breaking may
have been imperceptible.
But when the shearing and the dis
placement are sudden. agsregating ten
twenty or even fifty feet, thrusting BILL
lions of tons of rock out OF place, there
occur the Jars and tremors that make
the earth trenble over an area OF many
thousands OF square miles. II the dis
placement occurs little by little at in
tervals tho shocks may last for days
and even months. Not very much ad-
justrnent Is going on along the Appa.
lachian Mountains for these ranges are
old as mountain making goes. But the
great Cordillera which encircles the Pa
off]c Ocean Is comparatively young and
IL. folding and faulting are manifest In
the great number OF disastrous shocks,
especially in tho Andean ranges and In
the Japan chain Of islands.
The earthquake which wrought dis
aster to San Francisco in 1906 was due
TO thrusts and displacements along q
fault several hundred miles in length.
The character OF the displacements
upthrust here. slip down.
ward there. but always a rift with its
edges pulled apart. DR.. Omori, the Jap
anese seismographer. who is probably the
foremost authority on the subject. laid
especial emphssis on the fact that the
strain was diagonal. Roads. fences ana
walls lying across the fault were not
broken across; they were pulled
out OF alignment as well---in some In
stances six or eight feet.
The rift OF the Charleston earthquake
was probably quite as severe rs that OF
but the buildings were sub
stantial ana less damage resulted from
the shocks. The California earthquake
Of 1905 was not severer than that Of
1883, but the frame buildings were less
abls 10 resist the shocks after nearly
forty years of weathering. The CHIEF
cause of disaster in San Francisco was
not the shock; Il came from the break
ing Of the water mains which lay across
the fault.
In many instances displacemerts Of
the rock layer have created depressions
which in time became lake beds--some