The Bamberg herald. [volume] (Bamberg, S.C.) 1891-1972, 1906-06-28
CAUSE OF EARTHQUAKES
VIEWS OF PROFESSOR TARR,
AMERICAS SEISMIC AUTHOR
ITY

Was the Centre, She Is Still in Peril
Cornell GeoIogist Tells His Deduc-
tions from the Pacific Coast Disas-
ter.
Ralph Stockman Tarr, professor OF
dynamic geology and physical geogra-
ply at Cornell, and perhaps the most
noted authority in America on sels-
mic disturbances, telegraphed to the
New York Times his views on the
causes of the disaster at San Fran
cisco as follows:
Ninety-four percent Of all recorded
earthquake shocks occur in two mar
row zones following two great circles
of the earth. One of these passes
through the West Indies, Mediterran-
can. Caucasus and Himalaya regions,
and in this belt SO percent of all re-
corded earthr axes have occurred.
The other, which California lies,
encircles the Pacific, following the An
des, the mountains OF Western North
America, the Aleutian Islands, Japan,
and the East Indies. Forty-one per-
cent of all known shocks have oc-
Cured in this belt.
Other regions on the earth have sup
piled but 6 percent Of recorded earth
quakes, and these for the most part
were of slight intensity. Consequent
ly, areas outside these belts are in
slight danger of earthquakes. The two
zones Of recent shaking are also re-
gions of volcanic eruptions and grow
ing mountains.
The great majority Of the active
volcanoes of the earth lie in these
belts, and geological evidence proves
conclusively that in these zones the
mountains are still rising. These two
phenomena, volcanoes and growing
mountains, account for the vast major
ity of earthquake shocks. The move
ments of the lava and Of the pent-up
steam preceding and accompanying
volcanic eruptions send out tremors
and shocks through the earth. But
the most extensive and violent shak-
..::::s occurs when the rocks break or
move along previous breaks, called
faults. Then a succession OF jars
passes through the crust, often doing
great damage. Such movments result
from the strains to which the rigid
crust of the earth is subjected in the
process of mountain growth.
It Is too early to pronounce a final
opinion upon the nature and cause OF
the San Francisco earthquake, but
from what has been said it will be
seen that it is probable that this shock
is the result of movements along one
or more fault lines in the course OF
the natural growth Of the Coast
Ranges, which geologists have long
known to be still in progress through
out the entire extent Of California.
That the Coast Ranges are growing
is proved by numerous evidences.
There are upraised short lines at vari-
GUS points along the California coast,
proving recent uplift. The very bay
of San Francisco is the result OF
geologically recent subsistence OF this
part of the coast which has admitted
the sea into the gorge that the Sacra-
mento river formerly cut across the
Coast Ranges. This forms the Golden
Gate, and in the broader mountain
valley behind the sea has spread out
to form the bay.
A further reason for knowing that
the mountains of this region are grow
ing is the frequency Of earthquake
shocks in California. Every year
there are from 25 to 40 earthquakes
recorded In the state, and not a few
Of these have been felt in San Fran
cisco itself. For example, on March
30, 1898, there was a shock which did
damage to the extent Of $4,000 at the
Mare Island navy yard. The city Is in
a region of earthquake frequency, and
itself seems to be near line OF move
ment. Whether the centre OF greatest
disturbance Of the present shock Is IN
or near the city cannot yet be told.
though the meagre reports so far re-
ceived indicate this. If 1t IS, San
Francisco is in danger Of future dis
asters.
It is the experience in the study OF
earthquakes due to fault movement
that the slipping may extend through
a period of days before the strain IS
fully relieved. This was illustrated
in the Yakutat bay earthquake, which
lasted II days. Therefore, it need not
be surprising If the shock of yesterday
is followed by others, but this Is not
an absolutely certain conclusion, for it
is possible that the single slip com
pletely relieved the strain for the
time.
Some day-no one can tell when
the strain will again need relief, and
renewed slipping will occur, and with
it renewed shaking of the crust, the
violence of which will depend upon
the amount of slipping. It is neces->
sary result of mountain growth. This
instance is but one Of many thousands
on record, and from all accounts ar-
rarently not one of the greatest mag
, ritude. It has attracted our attention
~-&