462 University of California Pxtblications in Geology [Vol. 12 



of continuous stress and successive reliefs from the consequent strain. 

 In the interval between 1854 and 1868 the station should have moved 

 .058 X 14 = .812 meters in the direction 168° to the point F. In 

 arriving at B in 1885 the station was creeping northerly and had been 

 doing so since 1868p. It had thus moved in the direction 168° for 

 seventeen years at the rate of .058 meters per year. This gives us the 

 position of the station at D in 1868p. The line FD is therefore the 

 measure and direction of the rebound of 1868 for this station. This 

 creep continued in the same direction from 1885 to 1906a and brought 

 the station to E. From E it rebounded to C in 1906. But the move- 

 ment due to slip on the fault in 1906 was in the direction 306°, along 

 the line and could only have arrived at C by a transverse shift, 

 unless C be located too far south by reason of the assumption of 

 immobility for the Mocho-Diablo base. This second assumption, that 

 Rocky Mound participated in the sudden displacement of 1868, yields 

 results which are consonant with the behavior of other stations in the 

 region to the south, whereas the first assumption of stability in 1868 

 places it in an anomalous situation with regard to the behavior of 

 stations north of the Golden Gate. 



Bed Hill. — Red Hill is 19 km. distant from the fault to the east- 

 ward. Its position was determined in 1854, 1885, and 1906p. The 

 displacements found by these surveys were : .65 meters in the direction 

 232°, between 1854 and 1885, and .30 meters in the direction 215° 

 between 1885 and 1906p. These figures suggest that the direction of 

 movement was away from the fault and nearly normal to its strike. 

 This suggestion may, however, be fallacious and the station may have 

 followed a devious path. To illustrate, let A, B, and C, figure 12, be 

 the positions at which the station was found in 1854, 1885, and 1906p 

 respectively. We may first follow the path of the station for the 

 period after 1885. At this date the station was at B, moving northerly 

 by strain creep. I shall assume the rate of this creep to be the same 

 as that found at Tamalpais, or .058 meters per year. In the interval 

 of twenty-one years between 1885 and 1906a the station must have 

 travelled 1.22 meters and have been somewhere on the circle aa' , which 

 is drawn from the center B with the radius 1.22 meters. If now the 

 sudden movement in 1906 were wholly parallel to the fault, then the 

 line cC, dra'wn through C in the direction 144°, would be the path of 

 the station for that movement, and the point of intersection of cC with 

 the circle aa' would be the position of the station in 1906a. But the 

 sudden movement of 1906 involved, besides the slip parallel to the 



