CAUSE OF EHARTHQUAKES—HOBBS | 267 
rebound is based upon the assumption that there was a single line of 
dislocation—the visible San Andreas rift or fault—and that the dis- 
placement along this plane was entirely in a horizontal direction, 
1I9Z2 “1923 
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Map showing positions of subsequent large earthquakes. 
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that time. 
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A. Reproduction of the writer’s map published in 1909 to show the sequence of recent earthquakes at 
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the area to the westward being supposed to shear upon that to the 
eastward. This shearing strain, generated, according to the assump- 
tion, as the result of a current or of currents within the subcrustal 
region on directions parallel to the San Andreas rift, dragged, it was 
