The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1922-03-02


dow of a river, the flow of this mas
of earth and stone ever to the north
ward, can be measured. Sometimes
such a flow is much accelerated b.
the elastic rebound" known to thu
layman as an earthquake For exam
pie. Mt Tamalpais. a peak some 2OO'
feet high, northward across the Col
den Gate from San Francisco. moved
3.O4 meters approximately 10 feet in
o nOrthwesterly direction. from 1854 to
1906 due to strain creep In 1906, in
the few seconds Of the earthquake OF
April of that year. it slipped back 1877
meters rather more than half its So
year creep. but in south -easterly di-
rection. not in line with its previous
advance.
The lighthouse on the larger Faral-
lon island. off San Francisco, was
and one-half feeD northwestward be-
tween 1860 and 1906, and then. in the
earthquake of 1906. to have slipped
back 129 meters, but this time almost
due west of its new position. In other
words. the whole of the Farallon island.
and probably all the islands Of the
group. made these two movements.
Chaparral another point Of observa-
ton, moved almost as far during the
brief period of earthquake in 1906 as il
had by strain creep IN the so years
preceding The movement by creep
from 1856 to 1906 was 26l meters at
Chaparral. and the movement back. in
southwesterly direction by elastic
rebound in 1906. was 2.O6 meters
Other places. and whole groups of
places moved similarly out i'm varying
From all these movements
and the data concerning them, order
has been worked and the figures tab
uated furnishing the basis for the
Of the time and place of
other similar elastic rebounds should
my appear in that section.
Depth of Movement.
one of the important factors. of !
course. in all these observations and
studies, is the difference in soil char
lcteristics, the difference in the COM
position of the crust of the earth. In
some areas. the crust is so composed |
and constructed that it will endure a
much greater degree of tension, strain |
,reep, than will other areas, since
some forms of rock and some compost
ions OF earth will endure more strain
han others before giving way at the
breaking point When it is considered
hat some earth movements are of such
'ast weight as to he almost incompre-
lensible and others comparatively linn
ted in area and depth. the very close
observation and calculation necessary
,laces the new method of forecasting
m a par with the study of the most
Instant stars. In the seismic disturb
nee of April. 1906. on the California
.oast. for example an area of approx
nately $1,000 square miles. moved to
maximum depth of 65 miles. That
S to say. about $751; cubic miles of
arth moved and its movement a:
ONE points was as much as - feet
assening. as the distance of the point
rom the main rift or fault increased,
% one foot
So important does the University OF
alifornia regard this discovery by
Dr. Lawson that the board of regents
as appropriated $4,000 for the pur-
base and installation of special in
irument for the work in the Lick OBJ
slvatory of the university. on MI. ,
hamilton, and stations for the Obser
alton of the strain creep along the
lmous san Andreas rift have been
established and observations are being
ken there daily. on Mt. Hamilton.
are made nightly while at
lah. other observations of the strain :,
eep of the skin of the world are be
e taken both day and night The :
strument to be installed on Mt Ham
on is Ross Photographic latitude =,
Iescope, which by photographing the :,
suits of its automatic observations.
inmates to a large extent the factor =,
human error found in the results OF =
'ual observation. Dr.. Lawson. W. W ?.
mpbel, director of the Lick observ.
1ry and r. II Tucker astronOmer -
ire. are making continuous studies -,
the earth movement all along the =,
cific slope, tabulating the result and -,
reby establishing records from ~
ich all necessary data concerning -
strain creep tension and elastic -,
.ound of the earths crust may be W
lived for use in making forecasts of -
thquakes.
Study of Movements. III
.tudy of the possible movements of Tt
crust of the earth also are being ha
de with instruments set on fixed" tn
along the san Andreas ca
1t was along this line that the Tia
st of the earth weakened and gave
y in April 1906. Since the earth cal
we'd in different directions on either st
e of this rift, this is considered one Ter
The strategic positions for the study lar
earth creep. Two points-Olema. in dit
rim county, across the Golden gate Uk
Inward from san Francisco and av'