DISASTER AS VIEWED BY SCIENTISTS.
=Scientists are Divided Upon the Theories Concerning the
Shock That Wrought Havoc in the Golden Gate City--May
Have Originated Miles Under the Ocean--Growth of the
Sierra Madre Mountains May Have Been the Cause.=
The subterranean movement that caused the earthquake at San Francisco
was felt in greater or less degree at many distant places on the
earth's surface. The scientists in the government bureaus at
Washington believe that the subterranean land slide may have taken
place in the earthquake belt in the South American region or under the
bed of the Pacific Ocean. San Francisco got the result of the wave as
it struck the continent, and almost simultaneously the instruments in
Washington reported a decided tremor of the earth, and the
oscillations of the needle continued until about noon.
At the weather bureau the needle was taken from the pivot and had to
be replaced before the record could be continued. Other government
stations throughout the country also noted the earthquake shock, and
they agree in a general way that the disturbance began according to
the record of the seismograph at nineteen minutes and twenty seconds
after 8 o'clock. This would be the same number of minutes and seconds
after 5 o'clock at San Francisco, which accords entirely with the time
of the disaster on the Pacific Coast.
There seems to be no reason to believe the earthquake shock in San
Francisco had any direct connection with the eruption of Vesuvius.
That eruption had been recorded from day to day on the delicate
instruments established by the weather bureau at the lofty station on
Mount Weather, high up in the Virginia hills. This eruption of
Vesuvius did not disturb the seismograph even at the period of great
activity, but apparently Vesuvius and Mount Weather were like the
lofty poles of two wireless telegraph stations, and between them there
passed electrical magnetic waves encircling the earth. The records
made at Mount Weather were of the most distinct character, but they
showed disturbances in the air of a magnetic type and did not indicate
any earthquake.
In explaining the San Francisco trembling, C. W. Hays, the director of
geology in the geological survey, explained that earthquakes are,
according to modern scientific theory, caused by subterranean land
slides, the result of a readjustment as between the solid and the
molten parts of the earth's interior.
"The earth," he said, "is in a condition of unstable equilibrium so
far as its insides are concerned. The outer crust is solid, but after
you get down sixty or seventy miles the rocks are nearly in a fluid
condition owing to great pressure upon them. They flow to adjust
themselves to changed conditions, but as the crust cools it condenses,
hardens, and cracks, and occasionally the tremendous energy inside is
manifested on the surface.
"When the semi-fluid rocks in the interior change their position there
is a readjustment of the surface like the breaking up of ice in a
river, and the grinding causes the earthquake shocks which are
familiar in various parts of the world. The earthquake at San
Francisco was probably local, although the center of the disturbance
may have been thousands of miles away from that city."
Prof. Willis L. Moore, the chief of the weather bureau, in talking of
the records of the earthquake in his department, said:
"We have a perfect record of this earthquake, although we are
thousands of miles away from the actual tremor itself. There were
premonitory tremblings, which began at 8:19 and continued until 8:23
or thereabout. Then there was severe shock which threw the pen off the
cylinder.
"According to our observations here there was a to and fro motion of
the earth in the vicinity of Washington amounting to about four-tenths
of an inch at the time of its greatest oscillation. These movements
kept up in a constantly decreasing ratio until nearly half an hour
after noon.
"San Francisco may have been a long way away from the real earthquake
and merely have been within the radius of severe action so as to
produce disastrous results. It is quite likely, in fact, that the
greatest disturbance may have taken place beneath the bed of the
Pacific Ocean.
"If it resulted in an oscillation of the earth of only a few inches
there would be no likelihood of a great tidal wave. If, however, there
was produced a radical depression in the bed of the ocean, the sinking
of an island, or some other extraordinary disturbance, a tidal wave
along the Pacific Coast would almost certainly be one of the events of
this great disaster.
"There are apparently three distinct weak spots in the United States,
which are peculiarly subject to earthquake shocks, and we are likely
sooner or later to hear from all of them in connection with the shock
at San Francisco. There is one weak area along the southern Atlantic
coast in the vicinity of Charleston, another is in Missouri, and the
third includes the Pacific Coast from a point north of San Francisco
down to and beyond San Diego."
In describing the instruments at the weather bureau which make the
record of earthquakes, even when the movement is so small that the
ordinary person does not recognize it, Prof. Moore said:
"The apparatus we have is a pen drawing a continuous line on a
cylinder which revolves once every hour and is worked continuously by
clockwork in an exact record of time. It moves in a straight line when
there is no disturbance, and it jumps from right to left and back
again when there are serious oscillations of the earth. The extent of
these movements of the pen measures the grade of the oscillation. You
may think it is a fantastic statement, but this seismographic pen is
adjusted so delicately that it will register your step in its
vicinity.
"The instrument is mounted on a solid stone foundation and what it
registers is the effect of your weight pressing upon the earth. It is
easy to see, therefore, that the record we have obtained of this
earthquake shows a few preliminary tremblings, which seem to be
premonitions, for about four minutes, then a great crash which threw
the pen off the cylinder and finally a period of nearly four hours,
during which there were slight tremblings of the earth, this latter
period marking the readjustment after the actual shock."
Most of the scientists were inclined to believe that the boiling
process in the interior of the earth, although it goes on
continuously, is subject to periods of greater or less activity. This
activity may be, however, purely local, according to the scientific
theory, for otherwise there would be eruptions in all the active
volcanoes of the earth at the same time, and there would be
earthquakes in every one of the areas where there is liability to
seismic disturbances.
One government scientist in discussing the San Francisco earthquake
said: "If we could have been right here in the vicinity of Washington
a few hundreds of thousands of millions of years ago, we should have
seen earthquakes that were earthquakes. The Alleghanies were broken up
by great convulsions of the earth, and it is probable that this North
American continent of ours was rocked a foot or two at a time, causing
a tremendous crash of matter and the reorganization of the world
itself.
"The crust, while not necessarily thinner, is not so solid. In cooling
it has cracked and left fissures or caverns or jumbled strata of
softer material between harder rocks, so that it is peculiarly subject
to earthquakes."
Maj. Clarence E. Dutton, U. S. A., retired, the most famous American
expert on seismic disturbances, said it was probably the greatest
earthquake that has occurred in this country since 1868. He declared
that it undoubtedly would be followed by disturbances of less
intensity in the same quarter. He stated most emphatically that the
eruption of Vesuvius had no bearing whatsoever on the disturbance on
the Pacific Coast.
J. Paul Goode, a professor in geology in the University of Chicago,
attributes the cause of the Frisco earthquake to the Sierra Madre
mountains, but not in a volcanic way, for he also claims that lava had
nothing to do with the California shock. The shocks, he showed, can be
attributed to mountains without volcanoes in their midst. The Sierra
Madres are growing, he said, and for this reason they have shaken the
city of San Francisco. He says that the gradual growing of mountains
causes the underlying blocks of the earth's crust to slip up and down
and shape the top of the earth in their vicinity when they fall any
great distance.
His ideas upon the subject are: "I figure that the earthquake which
caused so much damage in San Francisco came from what we call the
focus of disturbance. This focus at San Francisco is seven miles below
the surface of the earth. As the Sierra Madre mountains grow, a
phenomenon which is constantly going on, the blocks of earth below
change positions; as a large block falls a series of shocks travels,
up and down much the same way as the rings in the water travel out
from the point at which a pebble strikes. When the vibration reaches
the surface crust a severe shaking of the country adjacent is the
result.
"From the actions of the earth in April of 1892, when such a severe
shock was felt in San Francisco, I have no doubt but that a second
earthquake will follow closely upon the one of yesterday, as the
second followed the first in 1892. In that year the first came upon
the 19th of April and the second upon the 21st."
Of 948 earthquake shocks that have been recorded in California
previous to 1887, 417 were most active in San Francisco. The
seismographs which record the merest tremors and determine the place
of the shock show that 344 have occurred since 1888. Half of the sum
total have occurred in the vicinity of the gate city and for this
reason it is believed that the severe shock of April 18 was the final
fall of a crust of the earth which has been gradually slipping for
centuries, causing from time to time the slight shocks.
The seismic physics of San Francisco and its immediate neighborhood
have engaged the careful study of physical geographers. The commonly
accepted opinion is one which was formulated by Prof. John Le Conte,
professor of geology in the University of California, and one of the
world's geological authorities. His explanation is based upon the
mountain contours of the coast of California from the Santa Barbara
channel northward to the Golden Gate. In this region are represented
two peninsulas, one visible, the other to be discovered through
examination of the altitudes upon the map corresponding to existing
geological features. This second and greater peninsula comprises the
Monte Diablo and Coast ranges, separated from the Sierra elevation by
the alluvial soil of the low-lying valley of the San Joaquin. This
valley is contoured by the level of 100 feet and lower for a
considerable portion of its length, and practically all of it lies
below the level of 500 feet. The partition thereby accomplished
between the Sierra mountain mass and the coastal mountains is
sufficiently pronounced to indicate what was at no remote period an
extensive peninsula.
This valley of the San Joaquin lies above the line of a geological
fault, at a depth which can only be estimated as somewhere about a
mile. The artesian well borings which have been abundantly prosecuted
in the counties of Merced, Fresno, Kings and Kern afford evidence
looking toward such a determination of bedrock depth. On the ocean
side the continental shelf is extremely narrow. The great peninsula
presents a most precipitous aspect toward the ocean basin. It is
interrupted at intervals by deep submarine gorges extending close to
the shore.
The oceanic basin of the Pacific is throughout a region of volcanic
upheaval and seismic disturbance.
Conditioned on the one side by the known fault of the San Joaquin
Valley and on the other by the volcanic activity of the Pacific basin,
the greater peninsula of San Francisco in particular has always been
subject, so far as the memory of white settlers can go, to frequent
shocks of earthquake. In the last score or more of years seismographic
observatories have been maintained at several points about San
Francisco bay, and the records have been sufficiently studied to
afford data for comprehension of the varied earth waves which have
made themselves felt either to the perception of the citizens of the
Golden Gate or to the sensitive instruments. Such observations have
been conducted by Prof. George Davidson, for many years in charge of
the Coast and Geodetic Survey upon the Pacific Coast; by Prof. Charles
Burckhalter, of the Chabot Observatory, in Oakland, and by the staff
of the Lick Observatory on Mount Hamilton.
Careful inspection of these records shows that two systems of
earthquake disturbances act upon San Francisco. Those of the lighter
series show a wave movement beginning in one of the easterly quadrants
and more commonly in the southeastern. This series of light shocks is
attributed to the slip along the line of the San Joaquin fault. While
they may occur at any season of the year, they are more frequently
observed when the San Joaquin river is running bank high under the
influence of the melting snows in the foothills of the Sierra. That
such a condition has recently existed is made clear by the report
within less than a month of floods in the interior valleys of the
State. Assuming, as the geologists do, that the fault in the valley
lies near the roots of the Monte Diablo range, on the western edge of
the alluvial plain, it will be seen that the physical factors
involving the slip are very simple. There is a wide, flat plain
bounded on the west by a line of weakness in the rock supports. When
this plain is carrying an abnormal weight of water the tendency is to
break downward at the line of the fault. This tendency will produce a
jar in the mountain mass which will be rapidly communicated to its
farthest extremity.
The earthquakes which have their origin in the disturbances to which
the oceanic basin is subject always approach San Francisco from the
direction of the southwest quadrant. These have been uniformly more
violent than those whose origin is attributed to the San Joaquin
fault. While the records of San Francisco earthquakes up to the
present have exhibited a mild type, the damage to property having
hitherto been slight, it would appear from the extent and violence of
the present temblor that both causes had for once united.
The possibility of such simultaneous action of the two known seismic
factors of the greater peninsula had been foreseen by Prof. Le Conte.
He stated that if at any time an earthquake wave of only moderate
violence should come in from the oceanic basin in sufficient strength
to jar the coastal mountain masses at a period when the San Joaquin
Valley was bearing its maximum weight of water the conditions would be
ripe for simultaneous shocks from the southwest and from the
southeast. In such a condition, while neither of the shocks by itself
would be capable of doing any great amount of damage to buildings in
San Francisco, the combination of two distinct sets of waves might
prove too much for any work of man to withstand.
In spite of the declarations of some scientists that there can be no
possible connection between the eruption of Mount Vesuvius and the
earthquake of San Francisco, others are inclined to view certain facts
in regard to recent seismic and volcanic activity as, to say the
least, suggestive.
There is one very remarkable circumstance in regard to all this
activity. All the places mentioned--Formosa, Southern Italy, Caucasia
and the Canary Islands--lie within a belt bounded by lines a little
north of the fortieth parallel and a little south of the thirtieth
parallel. San Francisco is just south of the fortieth parallel, while
Naples is just north of it. The latitude of Calabria, where the
terrible earthquakes occurred last year, is the same as that of the
territory affected by yesterday's earthquake in the United States.
There is another coincidence, which may be only a coincidence, but
which is also suggestive. The last previous great eruption of Vesuvius
was in 1872, and the same year saw the last previous earthquake in
California which caused loss of life.
Camille Flammarion expressed the opinion that the earthquake at San
Francisco and the eruption at Vesuvius are directly connected. He also
sees a connection between the renewed activity of Popocatepetl,
Mexico's well-known volcano, and the disturbance on the Western coast.
He says that, though the surface of the earth is apparently calm,
"there is no real equilibrium in the strata of the earth," and that
the extreme lateral pressure which is still forming mountains and
volcanoes along the Western coast brought about an explosion of gases
and the movement of superheated steam several miles below San
Francisco, resulting in an earthquake.
Another theory is that the earth in revolving is flattening at the
poles and swelling at the equator, and the strata beneath the surface
are shifting and sliding in an effort to accommodate themselves to the
new position. Other scientists scout this idea, saying that
earthquakes are not caused by the adjustment of the surface of the
earth, but by jar and strain as the earth makes an effort to regain
its true axis.
As regards the possible connection between volcanoes and earthquakes,
it is known that a violent earthquake, whose shocks lasted several
days, accompanied the eruption of Vesuvius in the year 79, when
Pompeii and Herculaneum were destroyed. In 1755 thousands upon
thousands of people lost their lives in the memorable earthquake at
Lisbon, in Portugal. At the same time the warm springs of Teplitz,
Bohemia, disappeared, later spouting forth again. In the same year an
Iceland volcano broke forth, followed by an uprising and subsidence of
the water of Loch Lomond in Scotland. The eruption of Vesuvius in 1872
was followed soon after by a serious earthquake in California.
Coming to the present year, it is noticed that the earthquake in the
island of Formosa, in which 1,000 people lost their lives, was
followed by the eruption of Vesuvius on April 8. Soon after came the
second great shock in Formosa, in which there was an even greater loss
of life.
Later there were two earthquake shocks in Caucasia. At the same time
the news of this appeared there was a report of renewed activity on
the part of a volcano in the Canary Isles, which had long been
dormant. In the United States two volcanoes which have been regarded
as extinct for more than a century--Mount Tacoma and Mount
Rainier--began to emit smoke. In regard to Tacoma, Dr. W. J. Holland,
head of the Carnegie Institute at Pittsburg, says: "There is no doubt
that there has been a breakdown and shifting of strata, perhaps at a
very great depth, in the region of San Francisco. There certainly is
great connection between this earthquake and recent private reports
which have come to me of intense volcanic activity on the part of
Mount Tacoma."
On the other hand, leading scientists contend that these instances are
mere coincidences. "If there is any connection between Vesuvius and
the Caucasus and Canary Isles earthquakes other places would have
suffered too; New York, for instance, is on the same parallel," says
Prof. J. F. Kemp, of Columbia University.
Although each of these scientists has the most absolute faith in his
theory, he really knows no more about the facts than any boy on the
street. No one has ever descended into the interior of the earth and
investigated the heart of a volcano but Jules Verne, and he only in
his mind. What is needed now is exact information. The San Francisco
catastrophe will teach many lessons, and among them the necessity for
the close study of both volcanoes and earthquakes. There is no reason
why earthquakes and other internal disturbances cannot be observed
just as closely as the weather. In fact, it is entirely probable that
the time will come when a seismological bureau will exist for the
study of earthquakes, just as there is a Weather Bureau for
observation of the weather, and it will be the business of its
officials to prophesy and warn of approaching internal disturbances of
the earth, just as the weather men announce the approach of bad
weather. Government observation stations will be established, exact
records will be kept, and in the course of time we shall learn exactly
what earthquakes are and what are their causes.
Among other lessons that the disaster has taught is that the
much-maligned skyscraper is about the safest building there is. Its
steel-cage structure, with steel rods binding the stone to its wall,
has stood the test and has not been found wanting. Of all the mighty
buildings in San Francisco those of the most modern structure alone
survived. Their safety in the midst of collapsing buildings of mortar
and brick argues well for like structures in other cities.
[Illustration: Copyright by R. L. Forrest 1906.
=CHINESE REFUGEES IN WASHINGTON SQUARE PARK.=
It was estimated that as many as 10,000 Chinese were in this park at
the time this photograph was taken.]
[Illustration: =FLAT BUILDING SUNK INTO EARTH.=
A view of the great fissures in earth caused by earthquake. One story
of the flat building on corner sunk into the ground. The water main
was broken, which cut off the water supply. No water to fight the
fire or quench the thirst.]
Mr. Otis Ashmore declared that the regions lying along the Pacific
coast contain several of the moving strata which cause earthquakes. He
said:
"While much concerning the origin of earthquakes is still a matter of
doubt in the minds of scientific men, it is now generally conceded
that the real cause is the sudden slipping and readjustment of the
strata of rocks with the crest of the earth. As the earth is slowly
cooling a very slow contraction of the earth's crust is constantly
going on, and as this crust consists very largely of stratified layers
of rock, the enormous forces arising from this contraction are
resisted by the solid rock.
"Notwithstanding the apparent irresistible nature of these layers of
rock, they slowly yield to the enormous lateral pressure of
contraction and gradually huge folds are pushed up in long mountain
ranges. Usually this process goes on so slowly and gradually that the
yielding of the rock masses takes place without noticeable jar, but
occasionally a sudden slip occurs under the gigantic forces, and an
earthquake is the result. This slip is usually only a few inches, but
when two continents fall together for only a few inches enormous
energy is developed.
"Such slips usually occur along the line of an old fissure previously
formed, and the depth below the surface of the earth varies from one
to twelve miles. Thus places situated near these old internal fissures
are more likely to experience earthquakes than those farther away. It
is a well known geological fact that the Pacific coast in California
contains several of these fissures and earthquakes are more common
there. The entire western part of the United States has been slowly
rising for many centuries, and the shifting of soil due to erosion and
transportation doubtless contributes to produce these seismic
disturbances.
"Earthquakes are more common than most persons think. Modern
instruments for detecting slight tremors within the earth's crust show
that there is scarcely an hour in the day free from these shocks. In
mountain regions, and especially in the highest and youngest
mountains, erosion is most rapid, and on the sea bottom, along the
margin of the continents sedimentation is greatest. In these regions,
therefore subterranean temperature and pressure changes are most rapid
and earthquakes most frequent.
"A study of earthquakes develop these general facts. The origin is
seldom more than twelve miles below the surface; the size of the
shaken region bears a certain relation to the depth of the origin or
focus, the smaller shaken region indicating a relatively shallow
origin; the energy of the shock is approximately indicated by the area
of the shaken region; the origin is seldom a point, but generally a
line many miles in length; the subterranean stress is not relieved by
a single movement, but rather by a quick succession of movements
causing a series of jars.
"The transmission of an earthquake shock through the earth takes
place with wonderful rapidity. The elastic wave varies in velocity
from 800 to 1,000 feet per second in sand or clay to three miles per
second in solid granite.
"Sometimes these vibrations are of such a character as to be imparted
to the air, and their transmission through the air outstrips the
transmission through the earth and the ear detects the low rumbling
sounds before the shock is felt.
"If the origin of the shock is under the sea near the coast any
upheaval of the bottom of the ocean that frequently accompanies an
earthquake, gives rise to a great tidal wave that frequently inundates
the neighboring coast with much damage.
"While the phenomena of earthquakes and volcanoes are usually
associated in the same region, one cannot fairly be said to be the
cause of the other. Both are rather effects of a common cause, or
rather of common causes, the chief of which is the shrinking and
readjustment of the rocky strata within the earth. The suggestion that
there is some physical connection between the recent eruptions of
Vesuvius and the earthquake at San Francisco does not accord with the
generally accepted views of geologists concerning these phenomena.
"It is probably true that a critical condition of stress between two
gigantic and contending forces may be touched off, as it were, by any
feeble force originating at a distance. Thus a distant volcanic
eruption or earthquake shock may determine the climax of stress in a
given portion of the earth, which will produce an earthquake.
Observations show that more earthquakes occur near the full and the
new moon than at other times. This is probably due to the fact that at
these times the gravitation of the sun and moon are combined, and
their effect upon the earth is greater. We can see this effect in the
higher tides at new and full moon. But these forces, it will be seen,
are the occasions, and not the causes of earthquakes.
"The probable recurrence of the San Francisco earthquake is a matter
of great uncertainty. In general, whenever the internal stress of the
forces that give rise to earthquakes is relieved there is usually a
long period of quiescence in the strata of the earth, but in the
course of time, especially in regions of recent and rapid geological
changes, such as is the case on the Pacific coast, there is almost
certain to be recurrences of earthquake shocks from time to time.
"The geological forces may, however, gradually adjust themselves, and
it may be many centuries before such a dynamic crisis will arise as
that which has just convulsed a continent."
California has had a number of great earthquakes. The records go back
to the earthquake at Santa Ana in 1769. Not very much is known of this
earthquake, though a church was built there and dedicated as Jesus de
los Temblores.
Another one occurred at Santa Barbara in 1806, and still another in
1812. The Old Mission, about the only building there at that time, on
both occasions practically had to be rebuilt.
Hittell's History of California says that "slight shocks of
earthquakes are not infrequent, but none of really violent or
dangerous character has been known to occur. An old or badly
constructed building has occasionally been thrown down, and a few
people have been killed by falling roofs or walls. But there has been
nothing in the experience of the oldest inhabitants to occasion or
justify fear or dread. The first one of which there is any full record
occurred on October 11, 1800, and consisted of six consecutive shocks,
and it tumbled down the habitations of San Juan Bautista.
"The most disastrous shock occurred in December, 1812, when the church
of San Juan Capistrano was thrown down and forty Indians killed by its
fall. The same shock extended northwestward and damaged the churches
of San Gabriel, San Buenaventura, Santa Barbara, Santa Inez and
Purisima. In 1818 the church of Santa Clara was damaged, and in 1830
the church of San Luis Obispo."