708 WILLIAM HERBERT HOBBS 



TABLE I— Continued 

 DEFLECTIONS IN PRIME VERTICAL (AZIMUTH)— Continued 



located in the Atlantic Coast province (see below, p. 711), all are 

 to be found within the intense seismic area of the Pacific coastal 

 region, which was so recently, after the destructive California 

 earthquake of 1906, the subject of special investigation. When 

 now the stations showing notable anomaly are accurately plotted 

 upon the special map of the seismic province prepared by the 

 Earthquake Investigation Committee, 1 it at once appears that there 

 is an apparent relationship between their distribution and that of 

 the better-known recent faults of the province. The number of 

 stations with corrected anomaly of deflection greater than 50" is 

 something more than half (58 per cent) of the total number of 

 stations within the Pacific Coast province. In the map of Fig. 1 

 which shows the distribution of the abnormal stations (in dotted 

 outlines the map of the Earthquake Investigation Committee) 

 black circles of different diameters have been used to bring out 

 roughly the magnitude of the corrected residuals, and it appears 

 that those of higher order particularly are generally grouped near 

 the known displacements of the district, some of which have been 

 the seats of movement during recent earthquakes. 2 



Distribution of residuals in excess of 35" of arc. — Had the mini- 

 mum of abnormality of deflection been made 35" of arc, instead of 



1 A. C. Lawson, G. K. Gilbert, H. F. Reid, J. C. Branner, A. O. Leuschner, George 

 Davidson, Charles Burckhalter, and W. W. Campbell, Atlas of Maps and Seismo 'grams 

 accompanying the Report of the State Earthquake Investigation Committee upon the 

 California Earthquake of April 18, iqo6 (Carnegie Institution of Washington, 1908), 

 Map 1. 



2 The recent faults are not indicated on the area outside the dotted border. Few 

 gravity data relatively are available for the area east of California, where many fault 

 lines are shown. 



