876 L. MARTIN — ^ALASKAN EARTHQUAKES OF 1899 



3 



ber 10, 1899, at Yakutat Bay. In order to compare the duration and 

 magnitude of this Alaskan earthquake with that of San Francisco, Cali- 

 fornia, the record of Catania is also shown. The distances being nearly 

 equal and the paths equivalent, a direct comparison may be made. These 

 show the records from instruments in two planes at right angles and are 

 from heavily weighted vertical pendula with mechanical registration. 

 Eecords of the Omori horizontal pendula at Tokio as affected by the 

 earthquakes of September 3 and 10 are shown in plate 30. 



LOCATION OF ORIGIN FROM 8EI8M0GRAMS 



As early as September 27, 1899, Prof. John Milne located the origin 

 of the earthquakes of September 3 and 10 in Alaska.^^ He later made 

 the more specific location in the Pacific Ocean west of Alaska, near lati- 

 tude 50 degrees north and longitude 150 degrees west, noting on the 

 map^^ that the origin might possibly be moved 10 degrees to the east. 

 Dr. F. Omori located the origin of these earthquakes, making the latitude 

 60 degrees north, the longitude 140 degrees west.^* Dr. E. D. Oldham^^ 

 states that these shocks originated in latitude about 59° 5' north and 

 longitude 140° 0' west. Field studies in 1905 and 1909 lead to the loca- 

 tion of the earthquake origin in Yakutat Bay fiord. This is near latitude 

 59° 58' 20" north and longitude 139° 33' 0" west (see figure 5). This, 

 of course, assumes a single origin and places it along an old fault-line 

 associated with the 47i-foot uplift, the greatest observed change of level 

 of the land in 1899. It seems correct for the great earthquake of Sep- 

 tember 10. The origins of the other earthquakes may have been slightly 

 different and were perhaps not simple and single, but complex. 



INTERVALS AND TIMES OF MAXIMA 



From some of the best of the distant seismograph records Dr. E. D. 

 Oldham has computed the intervals and compared them with the ob- 

 served times of maxima of the three largest earthquakes.^^ 



M Nature, vol. Ix, 1899, p. 545. 



»3 Report of British Association for ttie Advancement of Science, 1900, pi. Ill, oppo- 

 site p. 77. 



^* Publications of Earthquake Investigation Committee in foreign languages, no. 5, pp. 

 61-65 ; no. 6, 1901, p. 51 ; no. 13, 1903, pp. 86-88. 



»5 Quarterly Journal of the Geological Society, vol. Ixii, 1906, p. 459. 



»' Unpublished manuscript. For a slightly different result with some of the same data, 

 see Report of the British Association for the Advancement of Science, 1900, p. 77. 



