THE 



POPULAR SCIENCE 

 MONTHLY 



AUGUST, 1906 



THE INVESTIGATION OF THE SAX FRAXCISCO 



EARTHQUAKE 



BY G. K. GILBERT 

 V. S. GEOLOGICAL SURVEY * 



T T is the natural and legitimate ambition of a properly constituted 

 -■- geologist to see a glacier, witness an eruption and feel an earth- 

 quake. The glacier is always ready, awaiting his visit ; the eruption 

 has a course to run, and alacrity only is needed to catch its more im- 

 portant phases; but the earthquake, unheralded and brief, may elude 

 him through his entire lifetime. It had been my fortune to experience 

 only a single weak tremor, and I had, moreover, been tantalized by 

 narrowly missing the great Inyo earthquake of 1872 and the Alaska 

 earthquake of 1899. When, therefore, I was awakened in Berkeley on 

 the eighteenth of April last by a tumult of motions and noises, it was 

 with unalloyed pleasure that I became aware that a vigorous earthquake 

 was in progress. The creaking of the building, which has a heavy 

 frame of redwood, and the rattling of various articles of furniture so 

 occupied my attention that I did not fully differentiate the noises 

 peculiar to the earthquake itself. The motions I was able to analyze 

 more successfully, perceiving that, while they had many directions, the 

 dominant factor was a swaying in the north-south direction, which 

 caused me to roll slightly as I lay with my head toward the east. 

 Afterward I found a suspended electric lamp swinging in the north- 

 south direction, and observed that water had been splashed southward 

 from a pitcher. These notes of direction were of little value, however, 

 except as showing control by the structure of the building, for in 

 another part of the same building the east-west motion was dominant. 



1 Published by permission of the director of the United States Geological 

 Survey and of the chairman of the California Earthquake Investigation Com- 

 mission. 



