14 SOUTHERN CALIFORNIA GEOLOGY 



Caledonia. The other extends east-west through 

 Europe and Asia Minor. There is no doubt but that 

 CaKfornia is included in the first-named group, 

 although seismicity is not so severe on this side of the 

 Pacific as on the other. There are other and older 

 zones of activity in parts of Central Asia, in Palestine, 

 along the Atlantic Coast and down the Mississippi 

 Valley. 



All but six per cent of the quakes of the world occur 

 in the two zones first mentioned, and most of these 

 upon the Asiatic side. About four thousand earth- 

 quakes are registered each year. Tremors from some 

 of them are felt throughout the earth. Some two hun- 

 dred or more, mostly too small to be otherwise noticed, 

 were recorded by the instruments at Pasadena in 

 1923. The latter were small vibrations from shocks 

 throughout the world as well as at home. 



SEISMICITY 



The liability of a region to earthquake shocks is 

 known as its seismicity. Japan and the east coast of 

 Asia in general is a region of intense and dangerous 

 seismicity. Other regions of the same kind, or even 

 more dangerous, are in Western China and Northern 

 India. History and experience show that the seismic- 

 ity of Southern California is relatively far less than 

 that of most localities within the great seismic belts 

 of the earth, where shocks, tidal waves and other dis- 

 asters have occurred of a severity far greater and of 

 more disastrous proportions than have ever been ex- 

 perienced on this coast during the residence of Euro- 

 peans here. And furthermore, as elsewhere shown, the 

 possibility of such occurrences here is most remote, 



