Haast. — jRecent Earthquahes on Land and Sea. 147 



Art. XXII. — On the recent Earthquakes 07i Land and Sea. 

 By Julius Haast, Pli.D., F.E.S. 



\^Read before the Philosophical Institute of Canterbury, 9th September, 1868.] 



[abridged.] 

 Before proceeding to make a few remarks upon the contents of the valuable 

 paper of Captain Gribson, to the reading of which we have just listened, 

 I think that some general observations on earthquakes, as experienced on 

 land and sea, their causes and effects, would not be here out of place. 



I should also like, with your consent, to test, by the observations which 

 we were able to make in New Zealand, some of the theories by which the 

 origin and propagation of these most formidable and greatest phenomena of 

 nature have been explained. 



The first sign of disturbance experienced in Christchurch was a slight 

 shock of an earthquake felt by several of our fellow-citizens in the early 

 morning of Saturday, the 15th of August, amongst whom, Mr. A. T. W. 

 Bradwell gave me, the same day, the best account. It was about 3 o'clock 

 in the morning that he felt a slight shock of an earthquake, travelling 

 apparently from S.W. to K.E., accompanied by a slight subterranean 

 rumbling sound. As buildings move generally in the direction from which 

 the vibratory movement reaches them, it is highly probable that this earth- 

 quake came from the N.E., from which direction the earthquake waves in 

 the sea appeared also afterwards on our coasts. 



There is no doubt in my mind that we can associate the earthquake 

 waves, in the sea at least, with the minor shocks experienced on the land. 

 Unfortunately, we do not yet possess the necessary data to calculate the 

 velocity of these minor shocks, which are without doubt the last pulsations 

 of a very severe volcanic earthquake, the focus of which is situated in a 

 N.N.E. or IST.E. direction from New Zealand. 



And I may observe here, that a volcanic central or linear earthquake 

 may be very severe at or near its focus, although its effects are confined to 

 a comparatively limited area round about it. Thus the slight earthquake 

 shock experienced in the early morning of the 15th of August, might have 

 been of a very local character only, although the disturbance on the sea 

 bottom, near its focus, was so enormous that the effects were felt, as far as 

 we know already, on the coasts of New Zealand, Australia, and the Chatham 

 Islands. And whilst the disturbance in the level of the sea, from the 

 impetus given, was such that it was felt over a tract of country several 

 thousand miles in diameter, the oscillations of the earth's crust may have 

 been confined to as many hundred miles only. Supposing that the Chatham 



