446 THE POPULAR SCIENCE MONTHLY 



THE EAETHQUAKE AREAS OF THE EARTH WITH 



SPECIAL REFERENCE TO THE RECENT 



ITALIAN EARTHQUAKE 



By Pbofessoe J. SHARSHALL GRASTY 



UNIVERSITY OF VIRGINIA 



THE recent Italian earthquake, which occurred on January 13 at a 

 cost of 30,000 lives and $60,000,000 in property, calls attention 

 to the fact that the most disastrous shocks of this sort are, in general, 

 not connected at all with volcanoes or volcanic areas. This is contrary, 

 of course, to the view widely held that all earthquakes are caused by, 

 or in some way connected with, volcanic activity. In disproof of this 

 view may be mentioned the great Calabrian earthquake of 1783. This 

 great earthquake occurred in southwestern Italy, but in no wise affected 

 the volcanic areas, and this is also true of the terrible Messina earth- 

 quake of 1908, which, though it devastated various towns and cities in 

 that part of Sicily not far distant from Mount Etna, arose from earth 

 movements in the Strait of Messina. It was not at all connected with 

 Etna, which at that time exhibited no unusual volcanic activity, and, 

 too, there were no other evidences that could possibly suggest its con- 

 nection with the earthquake just alluded to. 



The recent earthquake which first occurred east of Rome in the 

 Abruzzi district was followed by severe shocks in the province of Cala- 

 bria. Neither Vesuvius nor Etna is reported as exhibiting any special 

 activity. Indeed it is evident that they are in no way connected with 

 these shocks which have been so appallingly destructive of life and 

 property. 



Broadly speaking, there are two types of earthquakes, namely, the 

 volcanic, which is due to shocks accompanying volcanic explosions, and 

 the more disturbing and disastrous tectonic type, caused by faulting and 

 Assuring accompanying warping of the earth's so-called crusj;. In Italy, 

 these tectonic earthquakes, such as the Calabrian earthquake of 1783, 

 the Messina earthquake of 1908, and the recent earthquake that wrought 

 such destruction in the Abruzzi district are all of the tectonic type, and 

 all are the result of earth fractures brought about by mountain-making 

 movements. In this connection it will be of interest to consider just 

 what areas of the earth are affected in this way, and why, in certain 

 regions, earthquakes both occur and recur, while, on the other hand, 

 similar earth movements are not experienced nor to be anticipated in 

 regions where mountain-making movements are no longer actively in 

 progress. 



