THIRD REPORT OF THE DIRECTOR I906 



31 



RECORD OF EARTHQUAKES AT ALBANY 



APRIL 10 TO OCTOBER I, 1906 



Standard time 



Date 



Beginning 

 preliminaries 



Beginning 



principal 



part 



Maximum 



End 



Max. 

 ampli- 

 tude 



Multi- 

 plying 

 ratio 



Apr. 10 



Apr. 18 



Apr. 18 



Apr. 23 



Aug, 16 



Sept. 14 



Sept. 28 



h. m. 



4 29 p.m. 



8 21^ a.m. 



7 48 p.m. 



4 28 a.m. 



7 33 p.m. 

 II 37 a.m. 

 10 32 a.m. 



h. m. 

 4 41 

 8 32* 



7 47 

 10 36 



h. m. 

 4 4ii 

 8 35 



7 55 

 12 10 



h. m. 

 5 27 



'I 5 



8 



4 35 



9 

 I 13 



10 43 



mm. 

 35 

 65 



1 10 

 25 



12 



10 

 10 

 10 

 10 

 10 

 10 



April 10. A small but well marked disturbance probably a 

 preliminary to the earthquake of April i8 but possibly of Porto 

 Rican origin. The larger vibrations were registered on the north- 

 south pendulum, showing that they came from nearly an east or 

 west direction. The period of the maximum waves was about 24 

 seconds. The disturbance was recorded also at the Washington 

 and Baltimore stations. 



April 18. This is the violent earthquake which originated on 

 the Pacific coast, known as the San Francisco earthquake. It was 

 registered at all the seismological stations in this country and at 

 many places in Europe. The records obtained at Albany were ex- 

 cellent as the pendulums were in perfect working order at the time. 

 A comparison of the two tracings shows the east-west component 

 of the vibrations to be more pronounced, though a single long swing 

 in the north-south component had the greatest amplitude, 65 mm 

 as compared with a maximum of 48 mm in the former direction. 

 The duration of the preliminary tremors covered nearly the same 

 period as in the earthquake of April 10, indicating that both traveled 

 approximately the same distance. The slight disturbance in the 

 afternoon of April 18 was probably a reflex of the main shock. 



April 23. Faint vibrjations, but undoubtedly of seismic char- 

 acter. Main component was in an east-west direction. 



August 16. This earthquake originated near Valparaiso, Chili, 

 and was of even greater violence than that of April 18. The records 

 obtained show the strongest vibrations of any disturbance registered 

 thus far. The east-west component of the vibrations has the larger 

 am.plitude during the principal part of the disturbance, but the 

 north-south component is more marked throughout the entire period. 

 Near the beginning of the main vibrations, the pointer of the north- 



