Art. LV.—On the earlier Earthquake Waves observed on the Coast of New Zealand.
[Read before the Philosophical Institute of Canterbury, November 4, 1868.]
The vast extent of ocean over which tidal disturbances extended, caused by the late earthquakes along the coast of South America, have invested this subject with a degree of importance which they did not before possess, especially to those of us who live along the east coast of New Zealand. The object of the present paper is to place on record certain facts in connection with similar occurrences, which have been noticed in this country, in order that by degrees, as other facts shall, from time to time, be brought together, some light may possibly be thrown on the causes and effects of these remarkable phenomena.
The first great earthquake in New Zealand, of which we have any certain record, appears to have been that which occurred in October, 1848, and which was felt from New Plymouth to Wellington, and possibly at Auckland. In the South Island it extended from Nelson to Otago; but it does not appear to have done much damage excepting at Nelson and Wellington. This earthquake was felt at sea by a vessel, the “Sarah Ann,” at some distance to the north of Cape Farewell. No tidal disturbances appear to have been noticed.
Previously to this, in February, 1846, Mr. Hamilton, on a voyage from Auckland round Cape Horn, when about 1500 miles east of New Zealand, experienced a sharp shock of earthquake: the ship “David Malcolm” was in deep blue water, but she vibrated from stem to stern; some of the passengers supposed they were grating over a ledge of rocks.
The next great earthquake occurred on the 23rd January, 1855, and was felt over the greater part of the northern and southern islands of New Zealand; this again was felt most severely at Wellington, at which place Commander Drury, of H. M. S. “Pandora,” was anchored; I give extracts from his account of what occurred.
“At 11 minutes past 9 p. m., the north-west gale still blowing strong, we felt suddenly an uncommon and disagreeable grinding, as if the ship was grating over a rough bottom. It continued with severity for more than a minute; the ship slewed broadside to the wind. We were in 6 fathoms at the time.
“Lieut. Jones and myself immediately landed, we found the tide alternately ebbing and flowing. The gun at the flagstaff was turned over. The elemental wave proceeded from W. N. W. to E. S. E. There was no apparent disturbance of the barometer, or any apparent connection between the gale and the earthquake: we had however every reason to believe that the latter had immediate local influence on the atmosphere, producing violent gusts after the shocks. If it is a fact that the firing of artillery, or bush-fires, will produce a local calm by the disturbance of the atmosphere, the phenomenon here may be more easily accounted for. But a more interesting and extraordinary phenomenon occurred,—I say extraordinary, because no person appears to have noticed it in the earthquake of 1848; for eight hours subsequent to the first and great shock the tide approached and receded from the shore every twenty minutes, rising from 8 to 10 feet and receding 4 feet lower than at spring tides. Our ship I heard was aground four times at her anchorage. The ordinary tide seemed quite at a discount, for the following day, the 24th, it scarcely rose at all. On the 25th we weighed for Nelson, and felt one shock in 26 fathoms, off Sinclair Head (exactly the same feeling as when at anchor), and a slighter shock, in 80 fathoms, off Queen Charlotte's Sound.”
At Nelson the shocks appeared to come in a N. E. direction. At Canter-
bury, where the shock was severe, no damage whatever was done; nor do I believe that any tidal wave was noticed on the sea coast. A wave, however, came up the Avon to within two miles of Christchurch. I was at the time living close to the river, and heard the rushing sound of the water; I did not however know what it was until the next morning when I noticed that the river weeds had been washed on to the grass, for about one foot in height. It may be worth recording that a heavy rain from the north-west fell on the day of the earthquake; this is a very rare occurrence in the neighbourhood of Christchurch.
It is worthy of notice that earthquakes happened along the coast of South America at the same time, and were felt by different ships at sea in the neighbourhood of New Zealand. The earthquake waves in Palliser Bay were about 30 feet high, and showed a white crest although the night was cloudy; they succeeded the shocks. One family would certainly have been drowned had not some sailor, who had been on the South American coast, recognized the character of the approaching wave the moment in became visible.
A remarkable wave was observed some time during the month of March, 1856, by Mr. Michæl Studholme, who happened to be near the beach at the mouth of the Waiho river. He saw the wave at some distance in the offing, approaching from a south-easterly direction; it was many feet in height and broke with great violence on the beach, washing over into the lagoons which there line the shore; shortly after, on riding towards Timaru, he noticed the effects on the beach at different places. It does not, however, appear to have been noticed by any one at Timaru.
I happened to be at Akaroa some day during that month, and whilst engaged in surveying near low-water mark, was surprised to find the water suddenly rise, which it continued to do for some minutes, and then again began to ebb. I remember mentioning it at the time to some of the inhabitants of Akaroa, but not thinking of earthquake waves we attributed it to a change of wind in the offing sending in the tide before the proper time. This supposition would not, however, account for the ebb again commencing, and I now believe it was the same wave noticed by Mr. Studholme.
The recent earthquake waves have been so fully and ably reported upon by Captain Gibson, and our learned president, Dr. Haast, that it is not necessary for me to add anything to their observations.