Evening star. [volume] (Washington, D.C.) 1854-1972, 1906-01-21
SUNDAY MAGAZINE for JANUARY FL. 1906
ARTHQUAMES
Continued from page 6

| to the west coast OF North ana South
America Nearly all their earthquakes
originate beneath the ocean, and few are
| felt beyond the volcanic centers.
All volcanoes, with one or two pos
sible but somewhat doubtful exceptions,
are found near the ocean. Their bases
occur frequently at the top of steep
slopes, such as rise from the bottom of
the Pacific Ocean. Great earthquakes,
on the other hand, usually originate at
the bottom of these slopes, and are prob
ably due to the slipping and faulting
| Il. e. dropping DOWN of portion of the
rock strata. Sometimes this faulting
is actually visible, as occurred in Japan in
1901, when a great earthquake occurred
which devastated thousands of square
miles, and whose smaller vibrations were
| detected all around the world on the deli
cate seismographs which modern science
has produced. In this case a crack was
! formed which was visible on the surface
| for a distance of sixty miles. On one side
of this crack the ground sank in places to
depth of twenty feet, and doubtless at
lower levels the displacement was much
greater. Owing to submarine earth
quakes ocean cables are often fractured,
and in several instances the depth of the
ocean, as shown by soundings, has been
found to have increased by over a thou
sand feet.
1t is not merely near the ocean how
ever that violent earthquakes originate.
! Wherever steep continental slopes occur,
such as at the base of the Alps or in the
Himalayas, earthquakes are frequent.
This is especially true if the mountains are
of recent origin, geologically speaking,
and are still in process of elevation.
| While earthquakes usually originate at
the base of a slope, they sometimes start
higher up, and this is frequently notice
able in the Italian Peninsula. After a
severe shock, minor ones are often OBJ
served for weeks or even months in sue
cession. This is due to the occasional
slipping and gradual readjustment of the
strata to their new positions.
Besides the vertical changes of position,
considerable horizontal displacements of
ten accompany severe shocks. Thus
after the great earthquake of 1891 the
Japanese Government had to institute
a new survey of the region chiefly affected
in order to adjust taxation properly to
the altered conditions. The general eff
feet, while sometimes an expansion, was
frequently a compression, SO that when
new bridges had to be built the plans had
to be revised, to allow for change in
length amounting occasionally to one or
two per cent. Perhaps the most striking
change occurred in small plot of~land in
the most disturbed area, which before the
shock measured forty-eight feet in length
and afterward only thirty.
One of the most singular changes oc-
CURED in long narrow valley running
in a north and south direction, with high
cliffs on the eastern side. After the
shock the inhabitants all declared that
the sun was affected, because it now rose
at a later hour than it did before The
explanation really was that the floor of
the valley had sunk, and it therefore took
the sun longer to rise above the eastern
cliffs.
In the most disturbed districts during
this earthquake nearly every building fell,
it was estimated that over one million
| gravestoneS were overturned, temples