BAROMETRICAL FLUCTUATIONS AND EARTHQUAKES—FLUCTUATIONS IN TEMPERATURE
AND EARTHQUAKES.
_Changes in the barometer and earthquakes._—Mallet, who collected
together a number of examples of earthquakes which have occurred with
a fall of the barometer, and a number which have happened with a rise,
concludes that there are as many instances of the one as of the other.
At the great earthquake of Calabria, in 1783, the barometer was very
low. The earthquake of the Rhine (February 23, 1828) was preceded by
a gradual fall of the barometer, which reached its lowest point upon
that day. After the earthquake the barometer again rose. The earthquake
of February 22, 1880, in Japan, was accompanied by exactly similar
phenomena. Caldcleugh, who observed the heavy shocks in Chili (February
20, 1835), noticed that on February 17 and 18 the barometer fell 5/10
inches. Similar phenomena were observed before the succeeding smaller
shocks. After the shocks the barometer again rose. Principal Dawson,
speaking of the earthquakes of Canada, observes that some of the shocks
have been accompanied with a low barometer.
P. Merian, who examined the connection between the Swiss earthquakes
and atmospheric pressure, found that out of twenty-two earthquakes
observed in Basle between 1755 and 1836, thirteen of these were
local shocks, of which eight were accompanied with sudden changes of
pressure. Of the remaining nine, which were only felt slightly in
Basle, no change in atmospheric pressure was observed. Of thirty-six
earthquakes which, between 1826 and 1836, were felt in Switzerland,
thirty were chiefly confined to Switzerland, and ten of these occurred
with a low or falling barometer.
Humboldt is of opinion that earthquakes only occur with changes in
barometric pressure in those countries where earthquakes are few; and
he gives examples where the regular variations of the barometer have
gone on without interruption at the time of earthquakes.
Frederick Hoffmann, who examined fifty-seven earthquakes which occurred
at Palermo between 1788 and 1838, came to the following result:—
The barometer was sinking in 20 cases
„ „ rising in 16 „
„ „ at a minimum in 7 „
„ „ „ maximum in 3 „
„ „ undetermined in 11 „[113]
The observations of M. S. di Rossi apparently show that the earthquakes
in Italy chiefly occur with a barometrical depression and with sudden
jumps in atmospheric pressure.
Schmidt, who examined the earthquakes of the Orient, which occurred
between 1858 and 1873, says that they were rare with a high barometer,
but numerous when the barometer was low.
From an examination of a table of 396 earthquakes (May 8, 1875-Dec.
1881) felt in Tokio, furnished to me by Mr. Arai Ikunosuke, the
director of the meteorological department, I obtained the following
results:—
The barometer was rising in 169 cases
„ „ falling in 154 „
„ „ steady in 73 „
„ „ below the monthly mean in 189 „
„ „ above „ in 192 „
From this it would appear that in Japan at least the movements of the
barometer do not show any marked connection with the occurrence of
earthquakes.
When considering this question we must remember the marked effects
which a lowering of the barometer produces upon certain volcanoes and
solfataras. The volumes of steam emitted from Stromboli and from some
of the solfataras in Tuscany hold a marked connection with atmospheric
pressure as the quantity of fire damp given off from coal seams—these
being greatest when the barometer is low. At certain changes of
the weather it is said that the volcano of Vulture, near Melfi,
emits noises. These phenomena at once place volcanic phenomena and
barometrical pressure in direct relationship.
_Changes in temperature._—If, with an earthquake, it should happen
that there is a change in the height of the barometer, we should
naturally expect that this might be accompanied with the changes in the
temperature, in the wind, and in other atmospheric phenomena which are
more or less connected with the height of the barometer.
Many times it has been observed that after an earthquake there has been
a sudden fall in the temperature. Such was the case with the Yokohama
earthquakes of 1880.
Cotte endeavours to show that the earthquakes of Lisbon produced a
change upon the temperature of all Europe. In the year which followed
this earthquake storms were more common than usual.
Kluge has collected together a large number of examples when there has
been a fall of temperature at the time of an earthquake.[114]
At Kiachta, in Siberia, at the time of the earthquake of December
27, 1856, the thermometer fell from 12° to 25° R. We must, however,
remember that there are many cases known where the thermometer rose.
M. S. di Rossi remarks that we have the highest records of temperature
in the years richest in earthquakes. Thus, in 1873, at the time of the
earthquakes in Central and Northern Italy, an abnormal high temperature
was remarked. Japanese writers have remarked upon the unusual heat
which has shaken their countries. The temperature of subterranean
waters have been known to increase before earthquakes.