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PREEAC EH. 

The account of the California earthquake of April 18, 1906, contained in this 
report, exemplifies the spirit of codperation which pervades the scientific work in our 
day. Immediately following the great shock not only was the necessity of a scientific 
inquiry generally perceived, but it was realized that the occasion afforded an excep- 
tional opportunity for adding to our knowledge of earthquakes. The scientific men 
of the state, each on his own initiative, began the work of assembling observations ; 
the more intelligent citizens became persistent in their inquiries as to the nature of 
the earthquake, its extent and intensity, and the causes in general of such terrible 
disasters; and the state, thru its then Governor, George C. Pardee, unified the work 
of scientific investigation by the appointment of a committee of eight to direct the 
work. This committee was appointed on April 21, 1906, and became known as the 
State Earthquake Investigation Commission. On May 31, 1906, the Commission 
submitted a “Preliminary Report” to the Governor, which was printed and very 
generally distributed. In this report the details of the organization of the Commis- 
sion, the program of its work, and the results attained to that date are set forth. But 
while the Commission acted under the authority of the Governor of the State, no 
money was provided by the Government for the conduct of its work. The embar- 
rassment arising from this lack of funds was relieved about June 1, 1906, by a sub- 
vention from the Carnegie Institution of Washington, which enabled the Commission 
to prosecute its work as it had been planned. 
About the end of the year 1906, the greater part of the observational data having 
been collected, the work of sifting, codrdinating, compiling, and editing the same 
devolved upon the Chairman of the Commission. The results of this work, including 
several special papers by various investigators, are contained in Volume I, parts I 
and II, of the report and in the twenty-five maps of the accompanying atlas. In this 
volume especial effort has been made to give due credit to every contributor, whether 
he be a scientific writer discussing some particular phase of the general problem, or 
a citizen assisting with local information. In all cases where there is no ascription 
of authorship the Chairman of the Commission is responsible for the statements made. 
The multiplicity of contributors has made it inconvenient to duplicate their names 
in the already lengthy table of contents. 
In general, Volume I is a record of observations with quite subordinate discussion 
of the facts recorded. The effort to condense the record as far as possible has been 
tempered by the desire to omit no significant fact, so that the record may be as 
complete as possible for purposes of comparison with similar events which may occur 
in years to come. In the preparation of this volume the Chairman of the Commission 
gratefully acknowledges the kind advice and cordial assistance of Messrs. G. K. Gil- 
bert and H. F. Reid. The Commission is also under great obligation to its Secretary, 
Mr. A. O. Leuschner, for his very efficient services. 
Volume II is chiefly a discussion of instrumental records and of the data bearing 
upon the mechanics of earthquakes, by Mr. H. F. Reid, who also contributes a general 
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