Los Angeles herald., 1906-04-19

EXPOSED -

thousands of people were drowned. An
earthquake in the north Pacific in June,
1896, caused waves 40 feet high along
the northern coast of Japan that did
great damage, over $1,000 people being
drowned. Such an earthquake wave on
the coast of Peru once picked up gum
boat of the United States navy and left
it stranded mile inland. Earthquakes
are usually commonest In regions of
present or recent volcanic activity. In
the United States they are commonest
in California, and in general earth
quakes are more often felt near the
coast than inland, just as volcanoes are
more often found near the sea.
Earthquake Zone
At the same time there is seismic
zone encircling the whole earth in
which earthquakes are more numerous
than elsewhere and this zone does not
coincide with the distribution Of vol
canoes The zone includes Central
America, the West Indies, the Azores,
Italy, Syria, Persia, Afghanistan,
Tibet, Japan and Hawaii. 1t is by
some regarded as the real earthquake
center, since shocks in regious without
the belt are sometimes traced to dis
turbances within it. Thus the earth
quakes Of the Mississippi valley, 1912,
ceased when the volcano st. Vincent,
1000 miles distant, burst into activity.
The sounds that accompany earth
quakes have been variously compared
to the rumbling Of thunder, the clank-
ing of chains, sometimes loud sounds
accompanying slight shocks
AS earthquakes are frequently con-
nected with the eruptions of volcanoes.
and are common in volcanic regions,
many observers have thought that
earthquakes were volcanic phenomena.
Cause of Tremblors
This view was first expressed nearly
1000 years ago by Pliny, and during the
first half of the nineteenth century was
held by many biologists, including
Won Humbolt. From the fact how
ever, that many earthquakes in the
countries about the Mediterranean, in
California, and elsewhere. are not ac-
companied by any volcanic activity, and
since any great shock or heavy blow
within the earths crust would be
propogated by undulatory impulses, to
the surface, causing an earthquake, 1t
is now generally recognized that earth
quakes are due to variety of causes.
It is plain that some earthquakes are
due to the explosions of steam, that
are the chief characteristics of violent
eTupIlOnS. Illus Iue LSIIllC
explosion that tore off the greater part
of the island Of Krakatoa QS83). was
the cause Of violent earthquake.
Earthquakes frequently precede vol
canic outbursts and cease as the erup-
ton begins. Again 1t is possible that
in regions of present or recent volcanic
activity when no volcanic outbreak ac-
companies or follows an earthquake the
latter may have been caused by move
ments of molten rock deep underground.
Mountain Building
The sudden explosion of such rock,
If pressure were relieved by the open
ing of some fissure, as in the forma-
tion of dikes, might cause a severe
earthquake. In regions remote from
volcanoes it is possible that earthquakes
are caused by the same stresses In the
earth's crust, partly due to secular
contraction, that tilt and fold rock
strata into mountains. The strains to
which the rocks are thus subject when
suddenly relieved by the rock giving
way produce many earthquakes In
fact, the slight earthquakes of fire.
quent occurrence in the Alps. Hima-
layas, and in Southern Oregon, indi-
cate that mountain building Is still In
progress. The seismic zone that en-
circles the earth is. therefore, simply
a zone of weakness in the earth's crust,
within which crustal movements are
frequent.
Earthquakes in the regions remote