Popular Science Monthly/Volume 74/February 1909/The Latest Calabrian Disaster
|THE LATEST CALABRIAN DISASTER|
By Professor WM. H. HOBBS
UNIVERSITY OF MICHIGAN
NOW that more reliable accounts have reached us of the terrible disaster to Calabria and Sicily, it is possible to discuss some larger facts which seem to be revealed with clearness. The grand eruption of Etna, the disappearance of the Eolian islands, and other equally improbable rumors, have ceased to be valuable scareheads in the newspapers. The death loss it is still too early to properly estimate, but on the basis of a well determined law of news reporting, it is safe to say that the larger of the estimates will be much reduced. Many that have been reported killed will eventually be classified among the maimed and wounded, and many communes now supposed to be in as great plight as their near neighbors, will be found either to have received but slight damage or even to have remained immune. Such has, at least, been the history of the earlier Calabrian earthquakes.
A number of large towns at first reported destroyed as a result of the Calabrian earthquake of September 8, 1905, the writer found on visiting them a few weeks later had escaped without injury of any kind. The reported death roll fell from many thousand to 3,000, then to 1,500, and finally to 529, the last figure, that of the official count by communes.
Yet, notwithstanding this history there seems no reason to doubt that the death loss from the recent shocks will mount far into the tens of thousands. The greatest of previous disasters from this cause within the same region occurred in February and March, 1783, at which time the death roll was 29,515 (as finally counted by villages) and the property loss $26,000,000. This was, however, one of the greatest earthquake disasters of history, for recent extended studies by Woehle have shown that Lyell's estimate of 60,000 for the deaths caused by the Lisbon earthquake of 1755 should be divided in half. In this instance the estimates of deaths which were made at the time ranged all the way from 25,000 to 150,000.
One can not read of the rush of Italy's king and queen to the succor of their pitiably afflicted subjects, and of their remaining among them with considerable danger to themselves, without realizing that there is much of the heroic in it. The traditions of an almost parental relationship to their subjects, have thus been well maintained through the inspiration of their presence and their magnificent personal courage. The actual conditions have been terrible enough, but apprehensions of phantom dangers flourish amid ignorance and superstition, and in Italy the inspiring example of the sovereigns is hardly less important to operations of succor than are the rescue corps and their supplies. It was the writer's fortune to follow somewhat closely in the footsteps of King Victor Emanuel and Queen Helena after the Calabrian earthquake of 1905, and again after the Vesuvian outbreak of the following year, on both of which occasions a similar impulse carried them at once to the afflicted districts. As a result of this experience the writer has only admiration for their conduct.
A further word may be added concerning the work of the troops which were then engaged in rescue operations, since their conduct has been unfavorably commented upon in some quarters. The writer had ample opportunity to observe their work and would submit that the army acted not only with vigor and effectiveness, but upon a thoroughly scientific plan. There is, therefore, every reason to believe that all which is possible will be done by the Italian government in the face of the much greater catastrophe which it is now facing.
It is, however, beyond Italy's power to properly meet this disaster without some help from the outside world. The first supplies of food and of hospital stores, it may be expected, will be contributed in sufficient quantity, for the horror of the event has stirred the entire western world. The greatest pinch of poverty and starvation will come when the great wave of emotion has passed and the future a,lone is to be considered. To properly appreciate this, it is necessary to consider the normal economic conditions and the recent physical history of southern Italy.
Calabria and northeastern Sicily, the provinces affected by the earthquake, are overpopulated, and from them there has been much emigration to the United States and to South America. The chief sources of income are the culture of the olive, fig, the citrus fruits, and the cereals, and in Sicily the mining of sulphur. As regards fruit and cereal culture, the peculiar conditions of farm tenure are such that even under favorable circumstances a large part of the population is kept on the verge of poverty. The sulphur mining in Sicily is carried on in a small way over most of the interior, and until a few years ago was a fairly profitable industry. Now, however, the use of pyrites as a substitute for sulphur in the manufacture of vitriol, and the recent successful exploitation of the vast sulphur deposits of Louisiana, have so reduced the price of sulphur as to threaten the only means of livelihood of a large part of the Sicilian population.
In contrast to southern Italy, the conditions of living in the northern provinces are good, and it has long been necessary for the north Italians to contribute to the support of their compatriots in Calabria and Sicily. As a result of this burden, a strong party in the government has long been advocating a separation of the two sections, which would leave Calabria and Sicily to care for themselves.
To these discouraging general conditions must be added a series of special calamities which have befallen southern Italy since the summer of 1905. In September of that year, without warning of any kind, came the blow of the great Calabrian earthquake, the shocks of which destroyed property to the value of nearly $10,000,000, besides leaving a long list of killed and wounded. Both government aid and large private subscriptions from the northern provinces were necessary in order to succor the victims and in part to rebuild the mined villages.
In the following spring heavy rains largely ruined the crops in Sicily, and in April occurred the great eruption of Vesuvius which spread a mantle of ash on the flanks of the mountain, so as to bury the vineyards and remove for some years the sources of livelihood. Many thousand people who dwell upon the flanks of the volcano were thus thrown upon the government for support and the more favored Italians in the northern provinces were obliged to make further sacrifices for their relief.
What, we ask, is Italy to do in the face of the new disaster, following as it does so swiftly upon the heels of the others, and dwarfing them by its proportions. It avails nothing now to argue that much of the loss of life and property might easily have been avoided, had buildings suited to such a seismic district been constructed. This fact has again and again been pointed out by properly qualified persons after each fresh disaster, but the force of inherited tradition is not so easily turned aside, and it was only after the earthquake of 1905 that the beginning of better things was seen. Then in place of the loose stone and tile houses—veritable man deadfalls—which have again and again been raised over their own ruins, strong wooden barracks were constructed under government supervision. It is, however, only in such towns as were largely destroyed in 1905 that such reform measures have been adopted.
Leaving now the humanitarian side of this calamity we may turn to its scientific aspects. Enough is already known to state that the site of the heaviest movement lay in and about that small arm of the Mediterranean which separates Sicily from the mainland of Italy—a section of crust, therefore, which immediately adjoins upon the west that which was heavily shaken in the fall of 1905. This fact, no doubt, helps to explain the otherwise exceptional character, since a destructive earthquake is apt to be followed by a rather long period of comparative quiet, so soon as the so-called aftershocks have faded away. The great earthquake of 1783 possessed likewise this double character, but in that instance also the areas of the heavy shocks were distinct though adjacent.
For purposes of study the latest Calabrian earthquake appears to offer some exceptional opportunities. The peculiar outlines of the two land masses which are involved render them specially open to study from the sea as a base. The full importance of this fact will be appreciated by any one who has been compelled to find accommodations where only the ruins of hotels exist. Under such circumstances one must proceed on foot or with a donkey, carrying supplies of bread and wine with him.
A scientific party engaged in studying the Calabrian earthquake could live for most of the time upon a vessel from which the shore would be reached either at the numerous ports or by launches. If a government vessel is to be sent with supplies to the afflicted district, the opportunity should not be lost to despatch a scientific party aboard her.
For another reason the recent earthquake offers unique opportunities for study. It has long been known that the straight eastern coast line of Sicily corresponds to a great zone of faulting within the earth's crust, and more than once in the past the slips upon it have brought disaster. On at least one such occasion, the sea bottom between Messina and Reggio and between Charybdis and Scilla has been considerably modified. In the vicinity large strips of cliff have slipped down into the deep sea at their base. A primary object of a scientific party charged with the investigation of this earthquake should, therefore, be to carry out an elaborate series of soundings in waters within and about the straits of Messina. Fortunately the dangerous nature of this channel is responsible for accurate data which represent the late condition. We have, therefore, here the opportunity of determining by a simple re-survey the changes which are ascribable to the recent earth disturbance.
A second section of the expedition should have for its chief object the preparation of maps of all portions of the shores or inland areas which reveal any change of configuration as a result of the earthquake. One of the most difficult of questions which arise in connection with earthquakes is to determine the exact significance of the so-called "secondary cracks." These cracks are generally found in loose materials, and the question is in how far they represent the projection upon the earth's surface of cracks within the consolidated rock below, or in how far they are due to settlement, and have in consequence less significance of orientation. This question can be definitely settled only by the aid of careful and detailed maps, which are studied in connection with the fracture system of the more firmly consolidated rocks.
Either the same or a separate triangulation section of the party should have charge of the re-occupation of primary triangulation stations in order to see what changes in position and elevation of these stations are properly ascribable to the earthquake. It may well be doubted if more ideal conditions could anywhere be found for such a study. If continued changes should be found to occur during the progress of the surveys, as is by no means improbable, the opportunity thus offered to compare mass movements of the ground with the time of prominent aftershocks should be regarded as of the first importance.
In every great earthquake which is studied, perhaps the most important line of attack is found in the distribution of the surface intensity of the shocks. It is now everywhere acknowledged that this intensity or amplitude of movement (and it is on this that damage to structures depends), is in a large measure determined by the elastic or non-elastic nature of the underlying material. Amplitude of movement is least on so-called "solid rock," it is greater on non-coherent deposits such as alluvial material, and it is probably greatest over so called "made ground," with its tin-can and crockery ingredients.
With the passing of the centrum theory it is inevitable that the study of the immediate basement of each locality should enter upon the quantitative stage of development. The local quantitative effect of the surface layers is a factor which to an approximation may be known and for this reason should be eliminated, if the seats of movement are to be determined. Local thickness and relative elasticity of the unconsolidated materials in the basement must therefore, be determined, and the value thus obtained be deducted from the total local intensity, if we are to arrive at the genesis of the disturbance. Accurate geologic maps and earlier detailed seismological studies in Calabria and Sicily are favorable to an extended study of this subject.
There are few, if any, places where within a circumscribed area more elaborate magnetic observations have been carried out than about the straits of Messina. Before the earthquake of 1905 a detailed magnetic survey for this district had been completed. It is almost certain that large changes would be revealed by a new survey since it has been shown in Japan that important changes in the isomagnetics resulted from the great earthquake of 1891. The importance of magnetic records to earthquake study is each year being made more apparent.
A sixth object of study should be the tsunamis or "tidal waves" which apparently followed upon the recent shocks, since it has been demonstrated that such waves go out from the deeps of the sea apparently as the result of movements upon the floors of those deeps. That these movements are not directly connected with the land disturbances is apparent in their absolute lack of relation to such disturbances, even when the land disturbance is localized at and near the border of the sea. The California earthquake of 1906 was followed by no afterwave, though the Yakutat Bay (Alaska) earthquake of 1899 was succeeded by an inundating wave over forty feet in height.
Great deeps of the Mediterranean occur both to the north of Sicily (the Tyrrhenean deep on the site of a former land area) and also to the southeastward in the Ionian depression. Fortunately the land areas form a barrier between these deeps and furnish unusual opportunities of localizing the sea floor movements on the basis of the shore lines which have been washed by the wave. A series of soundings in these deeps, which have been already surveyed with considerable care, should afford a confirmative determination, provided changes not ascribable to errors in either series of soundings should be discovered. Such a discovery would certainly take foremost rank among earthquake investigations.
To sum up, therefore, it may be said that the proposed scientific expedition should be prepared to carry out at least six separate lines of investigation, since conditions are in all cases unusually favorable forstudy. These lines are: (1) a re-survey by soundings of the sea bottomseparating Sicily from Calabria; (2) the preparation of precise and accurate maps by expert topographers of all sections of the land which have suffered noteworthy visible deformation; (3) the re-occupation of primary triangulation stations in the vicinity of the straits of Messina, in order to determine changes in location and elevation; (4) the distribution of the damage on the land with due regard to the depth andl character of superficial deposits, and further comparison of the results; with those of earlier quakes within the same district; (5) a magnetic resurvey of the near shores (unless this is to be carried out by Italian workers); (6) the taking of a sufficient number of soundings over the great Tyrrhenian and Ionian deeps to determine whether changes in. depth explain the after-waves of the earthquake.
As precedent for such studies conducted upon foreign soil, it should be stated that the great Andulusian earthquake of Christmas Day, 1884, was studied by a French Commission headed by Professor F. Fouqué, sent out by the Paris Academy of Sciences. The same disaster was also successfully investigated by an Italian Commission sent by the Royal Academy at Rome, and our present knowledge of this earthquake is very largely based upon the monographs which were published by the French and Italian Commissions. There is, moreover, every reason to think that the Italian government would welcome and cooperate in every way with such an expedition as is here proposed. The present writer takes pleasure in saying that his studies of the Calabrian earthquake of 1905 were aided in every possible manner by the Italian scientific societies, and by individual seismologists.
There is a further reason why such a study should be undertaken by outside parties. It is difficult for one unfamiliar with the facts to understand the vexatious delays under which Italian scientists are often compelled to carry out their work. As a result of the financial straits in which the Italian government finds itself, the publication of scientific monographs is often long delayed. The manuscript of a report upon the Calabrian earthquake of 1894 had not seen the light when the shocks of 1905 arrived. This greater catastrophe seemed to render the report of less vital importance than a new report, and two separate royal commissions were appointed to prepare a report upon the disturbance of 1905. As their report has not yet appeared it is likely to be side-tracked for the report upon the new disaster. Thus the results of much painstaking scientific work see the light only in brief abstracts, because government action is too slow or, shall we say, seismic action too frequent.
- ↑ William H. Hobbs, I., "On Some Principles of Seismic Geology," with an introduction by Professor Eduard Suess; II., "The Geotectonic and Geodynamic Aspects of Calabria and Northeastern Sicily," with an introduction by Count de Montessus de Ballore. Gerland's "Beitraege zur Geophysik," Vol. 8, 1907, pp. 219-362, pis. 12.
- ↑ F. Fouqué et al., Mission d'Andalousie; "Etudes relatives au tremblement de terre du 25 décembre 1884 et a la constitution géologique du sol ébranlé par les sécousses," Acad. Sci. Paris, Mem., 2me ser., Vol. 30, 1899, pp. 1-772, pis. 42. T. Taramelli e G. Mercalli, "I terrimoti andalusi cominciati il 25 dicembre 1884," Atti della R. Accad. dei Lincei, Mem., 4th ser., Vol. 3, pp. 116-222, pis. 4.