The Story of an Earthquake
Tokyo, March 1st, 1887
The Times-Not appeared
On the evening of the 15th of last January, East Central Japan was convulsed by an earthquake of most unusual violence.
Originating near the eastern seaboard, in the hill region south-east of Tokyo, its vibrations extended over a land area of more than 27,000 square miles.
It shook up the inhabitants of the capital and Yokohama with a frisky energy which frightened even those hardened folks into something very like a panic.
It swayed and twisted houses, wrecked roofs, threw down chimneys, cracked walls, rocked furniture, and upset crockery.
Persons walking abroad felt the ground moving to and fro beneath their feet.
Vessels anchored in Yokohama Bay shivered so smartly that the hands below rushed on deck, believing that their craft had been run into.
In short, it was the severest and longest earthquake that had been felt in Japan for many years.
As such, it obviously offered a good opportunity for the collection of further data bearing on seismological research.
And the University authorities, fired by some of that seismic energy which Professor Milne contrives to breathe into all with whom he comes into contact, promptly despatched a Japanese expert to explore the field of action and report fully upon the phenomenon and its effects.
The gentleman chosen for this mission was Professor S. Sekiya of the Imperial University, a seismologist of considerable local repute.
He has carried out his task with that minute and painstaking fidelity which is usually shown by Japanese who have an allotted duty to do.
He tracked the earthquake to its source and followed it to its farthest bounds, collected a large mass of information, and illustrated his discoveries by a number of instructive drawings.
And all this was done so quickly that already, but six weeks after the event, we find him reading a paper before the Seismological Society, which, as a narrative of interesting details, confirming and illustrating in many particulars the theory of the subject, and pointing to some valuable conclusions, deserves a place of merit in seismic literature.
The story as told by Professor Sekiya is in no way sensational.
It is nothing more than a plain account of the short-lived exploits of an earthquake that only approached, without reaching, the dimensions of a catastrophe.
But its bearing upon a subject to which recent events in many parts of the world have drawn the attention of all mankind invests it at the present time with more than ordinary interest.
In The Times of the 7 th of January, it was pointed out that some eighty percent of Japanese earthquakes come along the seaboard.
The shock under consideration followed the prevailing rule.
A narrow axis or band of country, running near to the coast and nearly parallel to its general trend, for about thirty miles, and reaching the shore at Yokohama, is described by Pofessor Sekiya as the seat or origin of violent motion.
As in some former heavy shocks in this country, the area of destructive effect was found to be limited to a small breadth on either side of the axis, so that places as little as two or three miles to the north or south of it experienced a well marked deficiency of seismic energy.
The earthquake was preceded by the usual warning roar or rumbling, as of a distant cannon, emanating apparently from the western part of the central band.
Respecting the cause of the shock, Professor Sekiya believes it to have been a faulting or dislocation of strata in the earth's crust, a conclusion to which the geological and other physical features of at least the western half of this axial band lend considerable support.
If he be correct, we have in this case a variation from the probable most common cause of Japanese earthquakes, which, according to Professor Milne, is underground explosion of steam.
All along the central band, and more conspicuous in the western and hilly half than in the eastern, which is low table-land, the effects of the earthquake were strongly marked.
In the former, fissures and landslips were very numerous.
Professor Sekiya counted no fewer than seventy-two cracks in a distance of seven miles, one of them being a foot wide and five hundreds feet long, and all of them running parallel to the main axis of origin, which is also parallel to the main topographical features.
In the same region, which abounds with villages and hamlets, the effects generally reached their greatest intensity.
The sliding screens, covered with paper or of wood, which serve as doors, shutters, partitions, and windows in Japanese dwellings, were bent, broken, and shot out of their grooves.
The paper-covering or glazing of some partitions was rent and shivered in an extraordinary fashion, such as no other conceivable power could have brought about.
Houses were cracked, mutilated, unroofed, twisted, tilted up, and more or less wrecked.
Those of wood framing and heavily plastered suffered especially as to their walls.
Yet, strange to say, though thousands of buildings were left tottering on the verge of demolition, apparently needing but a puff of wind to blow them over, only two were actually levelled to the ground.
Several wells became turbid.
In some of artesian character the water decreased permanently or failed altogether; in others it increased.
One large river was so strongly agitated that the ferry boat could not be taken across it for some time after the shock.
The peasants say that they felt as if standing on waves of the sea.
Many persons were thrown down; and one scared countryman vouches to have been obliged to crawl on all fours, owing to the impossibility of walking upright.
To all these things were added the noise of the earthquakes' ruthless work and the shrieks of affrighted women and children.
At Yokohama the effects of buildings were corroborative of all that Professor Milne has from time to time told the world with regard to construction in earthquake countries.
Houses in that town are of so many types that they afford a fair field for comparison of results.
Most happily the intensity there was only one-third as great as in the hill region on the west.
Had the maximum intensity reached Yokohama, it is more than likely than not a chimney would have been left standing, and that, in the foreign quarter at least, there would have been heavy ruin and loss of life.
To sum up, the conclusions deducible on the recent occasion and confirming all previous experience, it is now more than ever clear that buildings of the composite construction common in this country, such as wood encased with brick or stone, are the earthquake's happiest play-ground.
They are embodiments of the cardinal error of rigid attachment of parts of a building which have different periods of vibration-i.e., which swing at different rates during earthquake shocks.
Houses of weak construction-for example, of thin brick-work or wood and plaster - and houses built of bad materials or on faulty principles, are also dangerous.
But the composite houses are mere earthquake traps.
Wooden structures, like the ordinary Japanese dwelling, are well enough - perhaps better than any as far as earhquakes alone are concerned, if thoroughly well constructed.
In Japan, however, fire is a more constant and even more dread enemy than the earthquake, and the latter often brings fire in its train, as a result of the overthrowing of lamps.
Sheet-iron houses, as used in Australia, would be strong, cheap, and effectual, but they have the drawbacks of ugliness, difficulty in providing against extremes of temperature, and danger from typhoons.
On the whole, it appears to be the conclusion of our seismologists that solid, heavy buildings of stone or brick, with their various parts well constructed, strengthened, tied, and bonded, on true principles of architecture, and with due knowledge of the strength of materials, are the best and safest for earthquake-ridden countries.
The forces to be dealt with are forces altogether independent of gravity, and for the most part act in a horizontal direction; and architects and builders must apply the resources of their arts accordingly.
Many valuable suggestions under this head, into which it would be tedious to enter here, are to be found in Professor Milne's paper on "Construction in Earthquake Countries," in the Proceedings of the Institution of Civil Engineers.
High-pitched roofs, heavy balconies, tall chimneys, and all other forms of top-heaviness are to be avoided.
Although Japanese temples, with their abnormally heavy roofs and relatively light supports, seem to be almost earthquake-proof, they owe their safety to the great number and elasticity of the joints in their sub-structure.
In the words of seismology's chief apostle, Milne, "Keep your weights low, and your roofs as flat as possible."
If Naples, with its piles of high top-heavy houses, were to be shaken by an earthquake as severe as the one under consideration, it is not too much to say that a large part of the city would be reduced to ruins.
Short, squat, strong chimneys, without heavy mouldings, are to be recommended.
Tall, projecting chimneys will surely come down, unless free to swing without connexion with the house.
Of the chimneys demolished in Tokyo and Yokohama on the 15th of January, nearly fifty percent were cut clean off at their junction with the roof, the wooden or composite house swinging much more quickly than the chimney.
The recent earthquake also furnished many corroborations of the accepted maxim that buildings on soft or made ground suffer more than those on hard, virgin soils.
At one village, Professor Sekiya found that in a long street only twenty feet wide much greater damage was done to the houses on one side than to those on the other, a difference attributable only to the fact that the former stood on artificially-made ground.
And, generally, villages built on soft soils felt the severest effects; while in Tokyo the ratio of disturbance on low, marshy ground to that on firm ground was as great as three to one.
Again, buildings situated on hill-brows and hill-sides were found to vibrate much more actively than those on a flat hill-top or at its base.
This well established fact respecting "marginal vibration" as it is termed, is being made the subject of systematic observation in Tokyo.
It is easy to understnd that the large free surface exposed in a hill-side must be highly susceptible to the horizontal throw of an earthquake.
In Tokyo, situated some miles from the axis of origin, the shock was felt only about one-half as severely as in Yokohama.
Here, however, the shakings of the ground came within the range of exact scientific measurement and observance.
It is thus recorded that the principal movements - i.e., those exclusive of preliminary and after tremors - lasted for more than two minutes, during which time no fewer than sixty distinct shocks occurred, at intervals of about two seconds.
In the greatest of these - which, as before remarked, took place in marshy ground-the horizontal range, or back-and-forth motion of the ground, amounted to eight-tenths of an inch, while the vertical component was barely one-fourteenth of an inch.
Though of large amplitude as well as unusual and alarming duration, the rapidity of these oscillations was not great enough to cause very much damage.
The comparative immunity enjoyed by the capital during the earthquake proper was extended also to the after shakes, only one of which was felt in Tokyo, while near the origin there were five shakes on the same night and four tremors on the following date.
To us who are constrained to dwell in the midst of so many and great dangers, on this unstable and highly heated domain of the earth's crust, it is some comfort to remember that, besides the practicable safeguards which have been indicated above, the patient researches, in other directions, of Professor Milne and his disciples have opened up to us additional means of providing against disaster from earthquakes.
Properly conducted seismic observations and seismic surveys may be made in the future to tell us not only what parts of a large country enjoy complete or comparative immunity from earthquake movements, and even what parts of a country or province are the securest districts for human habitation, but, yet further, to point out within the limit of a single city or town - nay, within as little as a few acres of space - the safest spots on which to build our dwellings.
This much learnt, we may largely reduce the amount of motion by isolating our foundation piers or walls from contact with the surrounding soil for a depth of a few feet only below the surface; or, under certain conditions, we may resort to the method of free foundations.
And, again, having discovered the quarter from which the motions are wont to proceed, we may strengthen our structures by due precautions as to materials and modes of building, and may plant them on the ground in that direction which will best avert evil consequences from shocks - that is to say, a square or oblong building will be most wisely erected with its diagonal parallel or nearly so to the line of motion.
However long it may be before the inhabitants of countries subject to earthquake movements will have the sense and the means to act upon the warnings which science gives them, we have here an epitome of all that human ingenuity has yet been able to devise for the protection of human life and property against one of the most potent and fearful of all forms of energy.
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