The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1856-1888, 1869-06-19
Earthquake Tides.

IL la long been observed that earthquakes most
frequently Cccur along the sea-cJa-t. and that IN
-uch cases they produce gigantic ocean tides
Sometimes the -ea bOils up and partly 0verfiOws
the land, but Oftcner IL rctirc- suddenly from the
shore. leaving harbJr- aDi bays bare and returns
again in irresistible force, ncaIei up like . solid
wall. 70 dash it-clf upon the coast These great
waves are more dreaded ~ maritime cities than
the earthquake shock itsc!E- They bear great
-hirs far inland they overthrow everything that
stands upright IN their course and- On their
backward IaS-age To- tue sea- they carry with
them % destruction men. animals. and property.
They mag bring dc-oiatiJn % localities WLeie the
earthquake itself Gls not been felt nor suspected.
The distance o. which these waves have been
prOIaSatei. and the rapitity with which the IN
pul-c moves have frequently been observed. Tie
recent enrthGuaEr- IN Peru and Bolivia afford a
striking instance. Mr.. Hpch-tctter has received
detailed information from New Zealand, which FER
init aJinc interesting calculations. lLc locus %
the earthquake was near tic Peruvian city 81
africa. where the first shocks were ieit AZ q quar-
ter past i've O'Clock in he afternoon o! the 10Th
Of August. Tie first earthquake tide arrived ia
the harb1r JT LytjlcJDn. New Zealand. at forty
i've minutes after four o'clock in the morning Of
the 18th Of August. ATicI J. 10 longitude ~ de-
grecs AMI - minutes West: Lyttlctpn a. village
ON the hlrLpr, sometimes called Port CO'Ier).
IN l72 degrees - minute East Tie difference
In lgngitude -. therefore, 243 teg. Is min rs
fleA IG-4HE AaAHf - llftAfAA' Va AN- H+
astronomical time, the difference ~ time between
the two places j. 10 hours and IL minutes. This
must be deducted from the apparent difference be-
tween the hour when the earthquake was felt ut
africa. and the hour when IT. tidal wave arrived
at Lyttlet0n. The apparent difference = 30
hOurs and 81 minutes the real time occupied by
the wave H ranNiu j., therefore, ~ hours and
l. minutes. The distance between africa and
LyttletOn i 10 degrees and IL minutes West
and - degree and ; minutes South. IN all about
! 900 miles, on y great circle. We lind, there
fore. that the earthquake tide travels some JOS
miles per hour, OF j4c feet Ter second. Ihis y
the r1piiity with which the impulse Of an Ortl-
nary tide or course VIC DO not mean the attrac-
the mJJn, which j. constant, AMI travels
30 O. speak. round the wOrd every twcnty-iOur
hOurs) j. prOIaguted over tie same route. In fact,
the pTDgre-- If the wave depends, not ut all on
the intensity Of tie original impulse, but on the
lcpth Of tic wItCr. accordingly We hnd from
observations that the earthquake tIdes Of
We have been Speaking Travelled with diff
rcreut yellciucs in different directions.
At ian Francisco. the velocity was about three
AMI sixty miles Icr hour IN some other
still les. The observations taken to-
,ether lead {, the belief that the depth Of the Pa
fife Ocean has been over estimated. Prof.. Hill
iarl, Of the United States Coast Survey, y max
NJ some calculations ON tire subject, which viii
interesting conclusions.
Before leaving the subject. We Will notice 4 fear
Nv TIC ufN~NaAIfA JIM AAt.H NW' AAb
4 the low coral islands living between South
america and Australia. IL j. supposed tlat. u
he waves which reached those far coasts were
enJngh, and strong enough To 0yerwlIclm
then they must have passed entirely over
be coral islands M their course. But tins rea-
CnIng J. erruueJus. The rise and TALL oil tides at
i'm deep water is almost imIeTceptiblc; and
heir vertical motion along shore depends ON the
lOpe Og tile bottom. Thus the difference between
igh and low water at the two most Elstcrly
apes North and South OfSayannah ON our Allan
IT, coast, i but one foot but this tide. transferred
horizontal into vertical motion, as 1t rushes
~ the slOping bottom I'm the >halDws along tie
cast. finally attains. mt Savannah. u rise Of seven
Now, the earthquake tide Of which we are
peaking travelled from africa to san Francisco ut
lc rate Of three hundred and sixty miles per hour:
nj san Francisco 10 was only two feet high,
MI the interval between the two successive crcsts
as one hundred and sixty miles. \ wave like
rat Is not recognizable rs q wave ut all. IL sim
" manifests itself n u gentle rise Of two feet,
flowed bv n subsistence and another rise IN half
n hour. The coral islands probably did not suf-
II from It's passage in mid-Ocean but ON reach
y and entering some confined hurbOr like those
I Port COOPER and the Banks Peninsula, il would
Sc width and gain height, and, rushing up along
sIOping bottom, would doubtless he able to
Ork. o. we arc informed it did, some damage To
llGges on the coast.
We are inclined to doubt the truth Of the state
ent, that the first phenomenon visible at Lyttle- (
N was an ebb. Perhaps the first How, coincid-
2 with ordinary tides, was not noticed. An ebb
c should think, must be the direct result Of an (
trtbtaakc, not the prOVagatsd effect vf rs tide. !
as there another earthquake. or 4 submarine {
rtbquake-wavc, transmitted IN the solid coast! !
I Sydney. the natural tide was running out {
hen the earthquake tide made its appearance, !
u q iO0d-tide began at mid-ebb. e
The numerous observations made IN different {
concerning, this great natural catastrophe I
u it, direct and indirect effects will furnish, d
zen cDllated ard discussed, an important addition -
the literature Of artlquakes.-AHrer'oaa ygRT- c
Z Of Mining.