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

per with them.
Speed Of Earth Waves.
From observations thus far recorded
it has been learned that the speed OF
the earth waves generated at the rift
or fault by the elastic rebound of the
earth's crust is approximately three
kilometers per second, or one and
seven -eighths miles per minute, rough
~ the speed of a very fast racing au-
tOmoble doing its best on a board -
| tracked racing bowl. While this wave
/ like motion passing through the crust
of the earth is too rapid for the hu-
man eye to see clearly. yet these swift
waves generate other waves of less
speed which are visible so that the
reports made by many observers that
they had seen the earth move like the
waves of the sea during an earth
quake are proved to be literally true,
though previously believed to have
been largely imaginative II also has
been ascertained that the length,
width and depth of fissures in the
earths surface, caused by earthquakes
are not accurate indications of the in
tensity of the temblor, because the
various formations of which the
earth's crust is composed react in
widely different ways to the force APP
piled by the elastic rebound during an
earthquake The stopping and starting
Of clocks also is an unreliable witness
strength of the shock, since some
clocks are 50 delicately adjusted that
shocks insensible to man will stop OF
start them, and others so heavily bal
anced that even disastrous shock
will not stop them, unless they are
overthrow. Dr. Lawson has estab-
lished that the first indication of an
earthquake of which man is sensible is !
the movement of liquid at rest in |
vessel. This phenomenon is almost |
always noted by careful observers be /
fore they themselves become physiO |
sensible of the shock. An /
other interesting discovery is that /
in general cause little or
no general change in altitude of tho /
areas affected. at least none of suffi- /
cient magnitude to be detected with |
certainty by observers or their instru-
nents.
Announcement From Berkeley.
Announcing these discoveries, the
University of California, at Berkeley,
mas issued a statement which dis
,usses them in part as follows:
1T is well known that. on the occa-
sion of the April 1906. earthquake,
he earth's surface stratum on the two
sides of the San Andreas fault line
This amounted, in the Bolinas region
north of San Francisco and the Col
len Gate) to as much as - feet and,
It many points, to II feet. That this
'elative displacement included areas
wing several miles from the fault line
vas shown conclusively for several
'ritical observing stations by the work
# the United States coast and geodetic
urvey shortly after the date of the
lntercomparisons of the
''AAN' III Aii1 RoHiAiOiio VI AltSt OD- /
CRYING stations made at different !
pochs left no doubt that earth move
nents on a general scale were init
lately connected with the earthquake {
henOmena of 1868 and 1906. In fact, t
esearches of this nature. made by A. l
=. Lawson. professor of geology at the $
University of California, have shown l
nat these earth movements are ante Il
edents. as well as consequences. of
lrthquakes connected with the san o
ndreas fault There is reason to be- Ii
eve that the suitable instruments To- $
lted comparatively near the fault i
ne would be capable of detecting the il
eeping of the earths surface stratum "
ON year to year To how many e,
lies from the fault-line motions of y,
lis nature can be studied to advan- cl
ge is uncertain, but the desirability al
securing such observations at crit >
al and advantageous points is very r
eat. Movements of the earths sur pl
ce of the nature described apparently pi
n be best detected and measured by az
ch programs of observation as those G,
the United States coast and geo We
tic surveys. and by suitable observa- ne
ms for the determination of geo. ~
aphic attitudes with extreme accu- n,
" in the critical region. 1t is like q
Sc well known that the ATTITUDES of IL.
points on the earth's surface are n
lerally undergoing change. The in tn
national latitude observatories at NJ
iah, in California; in Japan in 80
rkestan. in Italy and in Maryland. nj,
re shown the nature and values of ac
sc latitude variations. though the
Uses operating are. as yet only par ~
ny known 1e
Professor Lawson recently has 06'
led attention to the fact that the IN
dies of the latitude variation prob 70
by the astronomer royal for Eng fee
d, Sir Frank Dyson, reveal. in ad- II
on to the short period variations at %
iah a secular trend such that the 90
rage annual latitude of that station