Evening star., 1935-05-19
BY G. X. SPENCER.

b1 u. n. SfENCEh.
AS an American citizen, you are a
deputy earthquake observer" You
probably did not know that before,
but we're telling you now. Every
United States postmaster, from hum
BILE hamlets to great cosmopolitan
centers, has been instructed to OBJ
serve and report in a detailed manner
on all earth tremors in his bailiwick,
and to deputize you to do likewise.
The purpose is to obtain eventually
accurate knowledge Of the great
earth blocks which constitute the
United States, so that new kind
of map can be drawn. When this
map comes into being 1t is probable
that each Of the mighty sections of
the earth's crust which imprison and
float upon the central core will be
numbered in an orderly manner, so
that you can know just which blocks
you live upon.
A great number Of scientific pur-
poses also will be served. Since, like
the great mosaic Of an Arctic ice foe,
movements-or quakes-occur along
the edges of the great blocks, engi-
neers take laborious pains to avoid
drilling tunnels or mines across them.
With known block lines much costly
preliminary work can be avoided on
all structures from Office buildings to
great dams.
Can Improve Science.
Then, too, with known block lines,
geologists and seismologists can sta
ton seismographs and other instru-
ments along the lines. or faults" and
add another factor to the rapidly de-
veloping science Of actual earthquake
prediction.
Earthquake prediction Is coming,
but at first it will be something like
weather prediction by the United
States Weather Bureau-that is, in
fiuenced by many complicated factors
within the earth and out in space.
Mans science must still reach farther
ahead into the centuries before it can
become absolutely accurate. Move
ments along the fault lines which
mark the edges of the earth blocks
occur because the earth is still cooling
of; they occur often during the lunar
tides, for the moon creates a tide on
the land as it does on the seas, often
pulling the continents as far as Ct
feet apart.
w. c. Mendenhan, director Of the
United States Geological Survey, in
forms the writer that "a rather high
degree Of coincidence mas been shown
in the cycles of earthquake activity
and those of sunspots. This, in con-
nection with the visible relation be-
tween earthquake and volcano distri-
button, indicates a close relation be-
tween quakes and sunspot activity"
T. A. Jaeger of the Geological
Survey, in charge Of the volcano OBJ
servatory, Hawaii National Park, also
has traced a quite definitely close
relation between sunspot activity and
earthquakes.
New Field is Opening.
The above factors are now being
combined with others to set up a
science Of earthquake prediction, and
soon we shall have a new learned pro-
fession on this earth, with an enthu-
siastic body Of college trained prac-
titioners. These men will know some
thing Of astronomy, geology and
mining engineering; they will be tidal
authorities, too, and each will be
trained in the use Of seismographs,
tiltmeters and numerous other instru-
ments now in use and yet to be in
vented.
Astronomy will be important, for
when it is suspected that blocks in the
great "alligator's skin" which forms
the earth's crust have slipped a bit
past each other, astronomical bear
ings are taken. Slippages Of up to
18 feet in q century have been dis
covered.
In two places on the North Amer
ican continent fault lines are now
fairly accurately known; these are
California and that region just north
of the Great Lakes. Particularly is
this true Of the Southern California
fault lines, for which detailed maps
are now in existence.
You, as deputy observer, can help
this new science by reporting from
your vicinity significant "escarp-
mentS" which reveal risings in earth
blocks. Since the vast majority of
earthquakes are so gentle that they
cannot be felt by human beings, these
escarpments reveal what has taken
place.
Escarpments may be anywhere
from a few inches in height to per-
haps 20 feet, though on a greater
scale all mountain chains are mem
bers of the family.
Many people still fail to realize that
earthquakes are quite normal to the
earth'S crust and, in the United
States, a thousand times less danger
GUS for the citizen than merely walk
ing across a busy street. East of the
Rocky Mountains, the allowance for
wind resistance alone in a building is
more than would be required to pro-
vide safety for occupants. West of
the Rockies most buildings are now
earthquake-proof, and where they are
not they are rapidly being made so.
Ship Construction is Cited.
DR.. Kyoji Suyehiro, director of the
Earthquake Research Institute of
Japan and former naval constructor
OF the imperial Japanese navy, told
the writer that "if we can design and
build ships to carry the strains of
storms at sea, certainly we can design
and build earthquake-proof buildings
which, all told, are subjected to con-
Siderably less strain on the moving
land than that imposed on ships BY
storms at sea-"
Incidentally. in the case of our
largest city, New York, it seems al
most q fortuitous guidance of Fate
that 1t is recognized by geologists as
the safest spot in the Americas, if not
in the entire world, as regards earth
quakes, owing to its close-to-the-sur-
face, rigid bedrock.
In an exhaustive survey of the entire
United States, including historical rec
ords, as far back as 300 years ago, a
great insurance company established
the following expected average earth
quake damage" in cents per year per
s100 Of value in structures, and this
basis in actual figures reveals how
secure we may feel about earthquake
damage:
The Atlantic region, more than so