THE SEISMOGRAPH’S STORY

Dominion, Volume 19, Issue 86, 6 January 1926, Page 8

THE SEISMOGRAPH’S STORY

MONDAY’S SHAKE LOCAL MORE VERTICAL THAN HORIZONTAL Monday afternoon’s earthquake was certainly one that many people will remember for the rest of their days, as it, apparently, only had to continue a few seconds longer, or be a little bit more severe in its action, to bring about a great catastrophe, yet the record obtained from the seismograph at the Kelburn Observatory showed, according to Dr. C. E. Adams, the Government Seismologist, that the shake was only a moderate one, and not by any means what would be classed as severe, as it seemed to most people. The seismograph, however, cannot be wholly regarded as unfaithful, for it is a horizontal instrument, set to record lateral earth movements, more favourably when such occur from north to south or vice versa than from other points of the compass. Dr. Adams therefore concludes that the movement experienced on Monday afternoon was more vertical than horizontal in its action. Dr. Adams also stated yesterday that the shake appeared to be a purely local one, felt to a greater extent perhaps than elsewhere at Masterton, but also felt at Christchurch and on the West Coast to a slighter degree. In such a case the central point of disturbance is scarcely possible to locate. There are in existence instruments for registering vertical earthquakes, one verv expensive instrument being the invention of a former Russian Prince, but though experiments were being tried in various scientific centres to perfect such an instrument that will be within the reach of all observatories, the desired device has not yet been invented, so. that for the present the only recording instrument in New Zealand is designed to take horizontal movements on the earth, and onlv so much of the shake as is away from the di-ect vertical is recorded on the slowly revolving bromide paper. There are instruments the drums of which are geared to revolve at a faster rate and give a more detailed record of the jig-saw action of an earthquake, as far as it can be taken down by the mechanical pen, but tlie cost of sensitised paper has to be taken into consideration in running an observatory as with anything else, and the Wellington inst-unient is geared to run at a steady standard pace, which gives verv good results when the movement is more lateral than vertical. Visitors’ Experiences. The sensations of many people during Monday's earthquake were of a most unenviable character. . In the Government Tourist Department’s office were several visitors from England who, just off the boat,, were losing no time in arranging particulars of their tours. To most of these the earthquake was more than an experience. It was, to use the expression of one of them, “an unholy sensation. As the building began to rock violently, as though at the mercy of some great wave, fear was written large on the countenances of several of the visitors, and one at least of them stated broadly that he wanted to take the next .boat Home. However, they all very quickly ; recovered their composure, treating tlie experience as one to be proud of, and one likely to make them the envied of their friends in England. The full strength of the shake was most noticeable on the wharf. Men who were inside the Eastbourne Jerry Wharf office were living in expectation that the building would topple over. The rocking of the Customs Office was most pronounced. Its sway was most ominous. According to an engineer of one of the boats who took a line a®ng the waterfront, the sway of the wharf was quite four inches What the sway must have been at the top of the tall buildings may thus be . The manager of one office had a jug half-full of water in his room. The water became so agitated by the earth, cniake that some of it was spilt. What remained in the jug continued to move for some time after the tremor had apparently ceased. A window m a boot shop an Courtenav Place was broken. So far as is ascertainable, the shake was ' not noticed by people travelling in tramcars or in. trains.