EARTHQUAKE CAUSES.

Waikato Times, Volume 105, Issue 17752, 2 July 1929, Page 10

EARTHQUAKE CAUSES.

CONSIDERED BY EXPERTS. CONFERENCE WITH MINISTER. The probable causes of the severe earthquake of a fortnight ago have been discussed at a conference of experts convened by the Hon. H. Atmore, Min-ister-in-Charge of the Department of Scientific and Industrial Research, and an outline of the conclusions reached was given by Mr Atmore. It'appeared from the evidence so far gathered, said Mr Atmore, that New Zealand, being on a line of the world s crustal weakness, the earthquake was merelv a'normal manifestation of the releases of earth stresses, and that there was nothing exceptional in the phenomenon from the geological point of view. It would appear that the Arthur’s pass earthquake, the Murchison earthquake, the Hunterville earthquake and the recent one on the west of Cook Strait, were the result of a release of stresses along the same chief line of weakness, and to that extent those shocks were undoubtedly somewhat connected. Freedom In the Future. Certain members of the conference appeared to be of the opinion that the fact that the stresses had been relieved over such a wide area augured favourably for freedom from major disturbances along the same fault in the Immediate future. There appeared to be a certain amount of evidence that there had been, in addition, a movement along the fault or faults off the West Coast of the South Island at Murchison. A deep-seated earthquake would cause considerable vibration in that vicinity, but it would appear that the slips were merely/ caused by large horizontal oscillation and were not of volcanic or explosive .origin. Evidence was given by Mr F. W. Furkert, engineer-in-chief of the Public Works Department, that in many cases these slips had occurred near fault lines recently traced by an officer of the geological survey. It was considered advisable, however, that Messrs Fvfe and Ongley, who had previously surveyed geologically in that area, should proceed to the district for a survey to find the connection between slip-movement and known fault lines, and that the Public Works Department should resurvey the projected railroad previously surveyed to Murchison and Westport, to find out what movements had taken place on the opposite sides of the faults in that locality. Useful Observations. It was also considered advisable that the Lands and Survey Department should be asked to erect trigonometrical stations on opposite sides of the main active faults in New Zealand, so that evidence could be obtained of movements along those faults indicating strains which might possibly relieve themselves by earthquakes in the distant future. Such observations had been made in California in connection with faults, .and had proved useful. Dr. C. E. Adams, Government seismologist, had placed evidence before the conference regarding the distance of the various after-shocks from Wellington. Unfortunately, owing to the instrument having been thrown out of adjustment by the first shock, the distance of the main shock was not accurately determined. The distance of the after shocks indicated that those arose from adjustment of the various fault blocks over a fairly wide area. It was considered advisable that the information service regarding small premonitory shakes should be increased in promptitude and vigilance, so that a full record of the trend of earth movements could be kept continuously under observation. In addition, the conference was of opinion that an observing station should be established at Nelson to assist the observations of Christchurch and Wellington in the exact location of future small earthquakes, while a reliable portable seismograph should be kept ready 1 to put in the field at short notice so as to study the nature and origin of such earthquakes.

The Minister said he considered that the question of building construction from the point of view of safety from earthquakes should be the subject of close investigation and discussion by seismologists architects, engineers, builders, representatives of local bodies and the Public Works Department with a view to, designing a model set of buildings which would withstand the effects of earthquakes.

Relatively Free from Fatalities.

Mr Atmore further emphasised that New Zealand had been relatively free from fatalities through the direct effects of earthquakes, and said that if buildings were designed as contemplated the Dominion could be reasonably sure of freedom from loss of life In future. If, however, buildings were erected without due regard Lo the effects of earthquakes, it was certain that a heavy list of casualties might be expected should a shake occur in a more populous part of (he country. So far as school buildings were concerned, Mr Atmore, who is also Minister of Education, said he was holding up several plans until reports were obtained as to the adequacy of the precautions embodied in the specifications.

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