254 HOVEY— EARTHQUAKES : [April 24, 



down. Massive walls showed cracks from half an inch to two inches 

 wide. The double amplitude of the wave motion of the earth is 

 estimated at not more than one inch. Such an amplitude is small 

 when compared with the four-inch amplitude calculated by Omori^^ 

 for the earthwave of the San Francisco (1906) Cjuake, the 6 to 

 12-inch amplitude estimated by F. A. Ferret" for the earthwave at 

 Messina in last December's quake, or the one foot maximum ampli- 

 tude given by C. E. Dutton^^ for the Charleston earthquake wave. 

 These largest estimates were derived from effects in soft ground 

 and are probably excessive. 



From a geological standpoint the movements causing the King- 

 ston earthquake were less important than the changes in the earth's 

 surface that were produced by it. Surface evidence of the former 

 has not yet been discovered, but the latter are quite apparent. Be- 

 ginning in the city water front, a belt of Assuring and subsidence 

 skirted the eastern half of the harbor and returned along the inner 

 (northern) base of the Palisadoes. Opposite the city the zone of 

 disturbance forked, one branch maintaining the original direction 

 and passing through Port Royal, while the other curved north- 

 westward touching Ft. Augusta and dying out in the River Cobre 

 valley, eight to ten miles northwest of town. 



From soundings taken for Professor Brown, it was learned that 

 " in several places along the edge of the harbor the bottom had sunk 

 from old soundings of a fathom and a half to over six fathoms, 

 and that on the harbor side of the base of the Palisadoes a series 

 of step faults reached a maximum depression at the shore to the 

 north of four fathoms." Port Royal sank from 8 to 25 feet. 

 The zone of disturbance was from 100 to 300 yards wide, contain- 

 ing where exposed many fissures and craterlets out of which water, 

 sand and mud gushed to heights of three or four feet. The fissur- 

 ing was caused by the compression and expansion of the earth due 

 to the passage of the earthquake wave, but the cause of the sub- 

 sidence is not clear, for the harbor as a whole did not sink — only 

 an encircling belt. Perhaps solution of the soft limestone where 



""The California Earthquake of 1906," p. 307, 1907. 



" Am. Jour. Set., IV., xxvn., 327, April, 1909. 



'* Ninth Annual Rept. U. S. G. S., p. 269. Washington, 1889. 



