EARTHQUAKES IN NORTH AMERICA ' 



By B. Gutenberg 

 California Institute of 7 echnology 



[With 1 plate] 



During the past 10 years considerable progress has been made in 

 determining the seismicity in a given area — the frequency of occur- 

 rence, and distribution of earthquakes. Earlier investigations were 

 based almost completely on field observations, but now extensive use 

 of instrumental records is possible. This assures much more uniform 

 results for the whole earth. The use of seismograms in investigations 

 of seismicity was made possible by the development of methods which 

 permit a rapid calculation of a function of the earthquake energy 

 from instrumental observations. The first seismogram of a distant 

 earthquake that was recognized as such was made on April 17, 1889, 

 when an instrument at Potsdam wrote a record identified as that of 

 a shock in Japan. (Rebeur-Paschwitz, 1894, p. 436.) During the 

 following years instruments were designed which gave fairly good 

 records of distant earthquakes. In 1897, a committee of the British 

 Association for the Advancement of Science called attention to the 

 desirability of observing earthquake waves that had traveled great 

 distances. By 1899, 13 stations provided such observations and the 

 results were analyzed. In 1904 the number of stations reporting had 

 increased beyond 100, but less than half of them reported wave 

 arrival times reliable within about a quarter-minute. From that time 

 on, however, it has been possible to locate within a few hundred miles 

 all great earthquakes and most major shocks. In 1907 the Interna- 

 tional Central Station at Strasbourg issued the first catalog giving 

 all readings for the larger shocks reported for 1904. Thus, starting 

 with 1904, research on seismicity could be based on instrumental 

 observations. The systematic publication of such data was discon- 

 tinued during the First World War (when the catalog for 1908 was 

 in press) and later was resumed, starting with the data for 1918. 

 For the years 1912 to 1917 summaries for selected shocks were pub- 

 lished by the British Association for the Advancement of Science 

 under the supervision of H. H. Turner, University Observatory, 

 Oxford. 



• Reprinted by permission from Science, vol. Ill, No. 2883, 19.50, with added text and illustrations. 



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