THE EVOLUTION AND THE OUTLOOK OF SEISMIC 



GEOLOGY. 



(Plates XV and XVI.) 



By WILLIAM HERBERT HOBBS. 



(Read April 24, 1909.) 



Contents. 



Part I : Evolution of Seismic Geology. 

 Introduction. 



The Natural Development of Seismology Prevented by False Theory. 

 The Process of Averaging in Mapping Isoseismals and Coseismals. 

 The Evolution of the Fault-block Theory of Earthquakes. 

 The Relation of Earthquakes to Volcanoes. 

 The Mesh-like Distribution of Volcanic Vents. 

 Volcanic Extrusions in Relation to Block Adjustments. 

 A Possible Explanation of Volcanic Earthquakes. 

 The Conditions of Strain during tlie Growth of Block Mountains. 



Part II : The Outlook of Seismic Geology. 

 The Ultimate Cause of Earthquakes. 

 Earthquake Forecasts. 

 Periodicity of Earthquake Cycles. 

 Possibilities of Future Prognostication. 

 Need of Expeditionary Corps. 

 A Service of Correlated Earthquake Stations. 

 Preparation of Maps of Fracture Systems. 



Maps of Visible Faults and of Block Movements for Special Earthquakes. 

 Rate of Mountain or Shore Elevation by Quantitative Methods. 

 Investigation of Earthquake Waterwaves. 

 Conclusion. 



Part I: The Evolution of Seismic Geology. 

 Introduction. — Speaking generally, the present condition of a 

 science is so largely the consequence of an evolution by slow stages, 

 that if the past be reviewed the present stands revealed. Zoology, 

 which began with the encyclopaedists as a descriptive science, passed 

 into the comparative stage with the advent of Cuvier, and entered 



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