54 



Dr. C. Davison on Earthquake-Sounds. 



(1) The case in which no sound is heard has already been 

 considered in discussing the inaudibility of some earthquakes ; 

 and it is probable, as there suggested, that the absence of 

 recorded sound is due to the defective auditory powers of the 

 observers. 



(2) In the great majority of strong and violent earth- 

 quakes,, the sound-area occupies a region surrounding the 

 epicentre, while the disturbed area extends beyond it in every 

 direction. In Great Britain, the sound-area in our strongest 

 earthquakes is often considerable. In the Pembroke earth- 

 quake of 1893, the disturbed area contains about 63,600 square 

 miles and the sound-area about 37,700 square miles, being 

 231 miles long and 210 miles broad. The Hereford earth- 

 quake of 1896 disturbed an area of not less than 98,000 

 square miles, while the sound was heard over a district 320 

 and 284 miles in length and breadth and about 70,000 square 

 miles in area. The Essex earthquake of 1884 was felt over 

 about 50,000 square miles, and, excluding an isolated obser- 

 vation, the sound was heard as far as 114 miles from the 

 centre *. 



Similar materials for the earthquakes of other countries 

 are rare. In the Verny (Turkestan) earthquake of 1887, the 

 disturbed area is about 950 miles long, 560 miles broad, and 

 about 400,000 square miles in area ; the corresponding di- 

 mensions for the sound-area are 650 and 290 miles, and 

 about 132,000 square miles f. The Neapolitan earthquake of 

 1857, according to Mallet, was felt over the whole Italian 

 peninsula south of latitude 42° ; the sound-area was confined 

 to the neighbourhood of the epicentre, and contained only 

 3300 square miles J. Of another Italian earthquake, that of 

 March 12, 1873, the disturbed area measures approximately 

 670 and 430 miles in length and breadth, and 227,000 square 

 miles in area ; excluding one isolated place (Fiume), the 

 sound was heard over an area 236 miles long, 120 miles 

 broad, and 22,000 square miles in area §. In the Charleston 

 earthquake of 1886 the sound was heard at many places more 

 than 700 miles from the origin, and also at three places in 

 New Hampshire more than 800 miles ||. 



* R. Meldola and W. White, ' Report on the East Anglian Earth- 

 quake of April 22nd, 1884' (Macmillan, 1885). 



t J. V. Mouchketow, ' Le Tremblement de Terre de Verny, 28 Mai 

 (9 Juin), 1887/ Mem. du Comtie Geologique (St. Petersbourg, 1890). 

 The above figures are obtained by measurement from the map accom- 

 panying this memoir. 



\ ' The Great Neapolitan Earthquake of 1857/ vol. ii. pp. 287-288. 



§ These figures are deduced from records contained in A. Serpieri'e 

 ' Scritti di Sismologia,' parte i. 1888, pp. 44-97. 



''| C. E. Dutton, U.S.A. Geol. Surv., Annual Rep., 9th Rep. pp. 411-528. 



