Where ’Quakes are Born

Sun (Auckland), Volume III, Issue 704, 2 July 1929, Page 8

Where ’Quakes are Born

NATURE’S VAST STRUGGLES

ATTENTION is drawn to the origin of New Zealand by the recent severe earthquake shocks which have devastated first Arthur’s Pass, and now Westport and Murchison. Until a late period of the world’s development New Zealand was undoubtedly a scene of tremendous labour in gs by It is an interesting point whether this country, after the numerous volcanic struggles of which its formation hears trace, rests entirely at peace with the elemental forces of Nature.

Not since the Wellington earthquake of 1855, when the level land in the vicinity of the harbour was raised sft, has there been a disturbance approaching in intensity that of the West Coast ’quake, which was even more severe than that which spread consternation at Arthur’s Pass on the night of March 9. The earthquake which afflicted Murchison was probably as bad, at its origin, as the one which wrecked Japan in 1927, the difference being that its most violent manifestations were' spent on uninhabited country. The seriousness of earthquakes, however, is measured in terms of the damage which they do. Before the earthquake of 1855, the only previously noted one approaching it in intensity occurred in 1848. Other earthquakes between that time and the present have in some instances been markedly severe, and demolished chimneys and damaged buildings were by no means unknown along the recognised fault lines. WHERE THE FAULTS LIE

There is a large number of faults and fault-zones in the neighbourhood of New Zealand. There are several in the North Island, but the fault-system most likely to be of interest at the moment is the one which extends through North Canterbury, Marlborough, East Wellington and Hawke’s Bay. The valleys of Marlborough, and the lowlands of the Wairarapa and Hutt districts, are directly controlled by fractures of this great system. The Wellington ’quake of 1855 was caused by displacement along one of the major fissures. The southern end of the known active portion of the huge fracture-belt is crossed by several important east-and-west faults. Reopening of a fault extending along the upper valley of the Waiau-ua River was the cause of the Hanmer earthquake of 1888. About 200 miles east of the North Island lies the edge of the submarine plateau of which New Zealand is the

most elevated portion, extending in a north-easterly direction in practically a straight line for hundreds of miles. To the east, the sea floor is some thousands of feet lower, and in all likelihood the sheer edge of the plateau is the scarp of a great fracture-belt. Several earthquakes have originated near the southern end of this submarine scarp. There is another earthquake zone lying out under the sea, running some 50 miles from and parallel with the east coast of the South Island, from opposite Christchurch to southeast of Dunedin. Numerous ’quakes, of an unimportant nature, have emanated from this source. ’QUAKE RECORDING Since 1888 New Zealand has possessed a system of observing local earthquakes at about 80 selected telegraph stations throughout the country. Four seismographs, with photographic registration, are in the cquntry. One Milne and two Milne-Shaw seismographs are at the Dominion Observatory, Wellington, and the other, a Milne, is at the Christchurch Magnetic Observatory. There are also seismographs at Apia (Samoa) and Suva (Fiji). Even since the first European settlements were established in this country, shocks and shakes have gone on in various parts of the islands. The question must now be in the minds of many whether New Zealand is still free from the risk of earthquake disaster, or eruption. However, scientific observation has shown at least that the volcanic forces below are no longer capable of discharging lava, and are dying out. Earthquakes caused by earth movements alone are a different quantity, of course, but the fact remains that for long before the white settlers came populous native tribes lived in the land without that fear of catastrophe, as would undoubtedly have existed had violent earthquakes been common.