368 CARNEGIE INSTITUTION OF WASHINGTON. 



(2) Provision for a system of minute-to-minute standard time signals 

 recording simultaneously at all stations. 



(3) Provision for a set of seismographs recording in all three components 

 at Mount Wilson Observatory.^ 



Your committee also earnestly recommends the continuance of the support 

 hitherto given to the cooperative organization which has been effected both for 

 assembling geodetic, topographic, geologic, and submarine physiographic 

 data and for the further development of improved instruments of observa- 

 tion and measurement in this field. 



It is further recommended that Mr. H. O. Wood, Research Associate in 

 Seismology, be placed in charge of any stations that may be established. 



J. A. Anderson, 

 Ralph Arnold, 

 W. W. Campbell, 

 Arthur L. Day (Chairman), 

 A. C. Lawson, 



R. A. MiLLIKAN, 



Harry Fielding Reid, 

 Bailey Willis, 



Advisory Committee in Seismology. 



Carnegie Institution of Washington, 



October 1923. 



Willis, Bailey, Stanford University, California. Report on Chilean earth- 

 quake investigation. 



The methods and objects of investigation of the Chilean earthquake of 

 November 10, 1922, were initially somewhat obscure. No one knew the 

 character of the evidence which might be secured and no one knew exactly 

 what scientific or practical purposes might be served. There was, therefore, 

 a definite question as to what would result. Five months of field work demon- 

 strated the following outcome: 



On the scientific side the theory of elastic rebound as a prime condition of 

 earthquake vibrations has been confirmed. This theory originated in the 

 San Francisco earthquake of 1906 and was there developed according to the 

 geologic structure, which is characterized by vertical faults; and it was with 

 this structure in mind that I attacked the Chilean problem. It was found 

 necessary to modify the mechanics of the explanation by substituting a 

 nearly flat horizontal fault, situated 10 miles or more below the surface, for 

 the vertical faults recognized in California. The flat structure characteristic 

 of Chile was indicated by the enormous extent, some 300,000 square miles, 

 of the Chilean earthquakes, and the existence of the type of structure peculiar 

 to flat faults was evinced by extensive investigations in the Andes, up to 16,000 

 feet above the sea, and by detailed geological studies of the earthquake zone. 

 It follows that the Cordillera of the Andes is being pushed eastward by a force 

 which originates beneath the Pacific deep, and the mechanical structure of the 

 mountains, which are intimately related to the ore deposits, depending upon 

 the action of this pressure. This result has very far-reaching implications in 

 geophysics and also in mining. 



'Lawson dissenting. 



