.58 PROCEEDINGS OF THE ANX ARBOR MEETING 



DYXAMICS OF FAULTIXG AXD FOLDIXG 

 BY BAILEY WILLIS 



i Abstract) 



The direction of forces producing faults is considered and it is shown that 

 faults with a high dip require the action of vertical forces in combination with 

 horizontal forces. When we consider the influence of pressure on the strength 

 of rocks we find that horizontal pressure alone will always produce a fault of 

 dip less than 45 degrees. 



The forces producing folds are examined, and it is shown that the distribu- 

 tion of folds in the Appalachian region could not have been caused by simple 

 compression, but that forces acting tangentially on the under side of the folded 

 region must have existed. This idea is applied to the elucidation of the results 

 obtained by experiments in folding. An explanation of the nappes of the Alps 

 is suggested. 



Eead by title. 



CRITERIA FOR THE RECOGXITIOX OF ACTIVE FAULTS 

 BY STEPHEN TABER 



Read by title. 



FAULT MAP OF CALIFORXIA 



EY BAILEY WILLIS 



{AhHtldCt) 



Fault map of California : description and exhibition of a map of the State, 

 which shows the principal faults at present known. This map has been com- 

 piled from all available data by the Carnegie Institution of Washington, rep- 

 resented by Mr. H. O. Wood, the United States Geological Survey, the Univer- 

 sity of California, Stanford University, and the Seismological Society of Amer- 

 ica, working in cooperation, as a contribution to seismology of the State. 

 Active faults — that is, those on which earthquakes are liable to occur — are 

 distinguished from dead faults. The base is the relief map of the State, drawn 

 by J. H. Reushawe, of the United States Geological Survey, which brings out 

 strikingly the relation of the ranges to the active faulting. 



FAULTS OF THE CO A. ST RAXGES OF CALIFORXIA 

 BY BAILEY WILLIS 



(Ahstract) 



Faults of the Coast Ranges of California ; description of the various types 

 of faults recognized in the ranges : upthrusts, overthrusts, progressive thinist- 

 ing, regressive thrusting, transverse thrusts, and normal faults : vertical move- 

 ments of fault blocks involving rotation, protrusion, and depression ; horizontal 

 movements; relation of thrusting to folding; antiquity and actual activity of 

 forces; persistence of the structural type; magnitude of the structure; their 



