166 SOUTHERN CALIFORNIA GEOLOGY 



mud volcanoes and now quiescent but recently active, 

 true volcanic craters. 



So far as I have observed the displacement along the 

 lines is subvertical and amounts to a step-down of over 

 one thousand feet to the southwest. This fault line is 

 a part of the line of greatest seismicity in South- 

 ern California. It is the site of the most frequent and 

 the severest of the earthquakes that have occurred 

 in Southern California in late years, the shocks of 

 which are sometimes felt in and accredited to Los 

 Angeles, although the nearest approach of this line 

 to the latter city is over eighty miles. 

 THE ELSINORE RIFT 



Another conspicuous scarp-making master-fault 

 zone of great displacement extends from just west of 

 Pomona southeast through the Elsinore Valley and 

 from thence on into Mexico. One hundred and fifty 

 miles of its path lies within the State of California, 

 and its continuation into Mexico is conspicuously vis- 

 ible for at least fifty miles south of the international 

 border, beyond which knowledge of it is lost in the 

 geologic terra incognita of that country. It crosses 

 the Mexican border twenty-five miles west of the 

 San Jacinto Fault. Its course almost exactly parallels 

 those of Cadiz, Newberry, San Jacinto and other 

 fault line members of the group. It is even possible 

 that its northern end does not cease at Pomona, but, 

 that after temporary concealment beneath the more re- 

 cent formations of the valley plain, it may continue into 

 connection with the great San Gabriel Fault of Kew, 

 which extends northwesterly through the San Gabriel 

 Highland. 



Altogether the Elsinore Fault is one of the marked 



