Page:Popular Science Monthly Volume 74.djvu/143

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139
TEE LATEST CALABRIAN DISASTER

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