1909.] OUTLOOK OF SEISMIC GEOLOGY. 271 



ments along secondary fault lines, which produced at least three (and 

 perhaps more) major blocks. . . . The first and largest of these blocks, 

 ... is apparently titlted upward toward the southwest. 



Accompanying this faulting was a minor fracturing apparently due to 

 local adjustments in the tilted blocks. Doubtless this minor fracturing is 

 much more common than our observations indicate, for it was discovered 

 in more than half our expeditions into the interior when we went out of the 

 valleys away from the sea coast. 



The evidence accumulated for the tectonic origin of earthquakes 

 and their inseparable connection with the process of faulting in rock 

 strata, has shown that seismology must be considered as a part of 

 tectonic or structural geology — that part, namely, which is con- 

 cerned with the recent and present-day history of the earth. So 

 soon as this fact receives general recognition, the field of study must 

 be added to that now explored by geologists. For their loss in this 

 quarter elasticians will be more than compensated by the enlarged 

 opportunities which are now offered them for studying earth waves 

 as they are registered at a distance upon the newly devised earth- 

 quake instruments. 



Recognizing, then, that earthquakes manifest the time of opera- 

 tion of these larger mass movements of the earth's crust which have 

 brought about changes in level as well as changes in horizontal posi- 

 tion in connection with faulting, it becomes necessary to place the 

 subject en-rapport with the latest that has been learned in the wide 

 field of tectonic geology. This treatment of earthquakes as a part 

 of tectonic geology was attempted by the present writer in two 

 monographs published in 1907 in connection with a description of 

 the Calabrian earthquake of 1905,^*^ and later, in the same year, in a 

 treatise upon seismic geology." 



Having in mind the fact that the traces of fault planes are but 

 rarely exposed to view, and in only a small percentage of cases 

 possible of determination from purely geological studies, the inves- 

 tigation of the Calabrian earthquake was directed toward deter- 

 mining whether, (i) there are lines or narrow zones of special 



" " On Some Principles of Seismic Geology," with an introduction by 

 Eduard Suess. " The Geotectonic and Geodynamic Aspects of Calabria and 

 Northeastern Sicily," with an introduction by the Count de Montessus de 

 Ballore. Gcrland's Bcitrage z. Geophysik, Vol. 8, 1907, pp. 219-362, pis. 1-12. 



" " Earthquakes, An Introduction to Seismic Geology," New York, 1907, 

 PP- 1-336. 



