THE EARTHQUAKE

Evening Post, Volume CXVI, Issue 61, 13 March 1934, Page 8

THE EARTHQUAKE

ORIGIN OUT AT SEA

EPICENTRE LOCATED

Eecords made by the seismographs which are installed in various parts of the Dominion have now been examined by the Government Seismologist, Dr. C. E. Adams, and these, in conjunction with the various reports which have been received and tabulated, enable something definite to be stated about last week's earthquake. One of the best of the soisniological records is that made at Takaka. The instrument there was overhauled a few days before the earthquake by Dr. Adams, who was visiting the West Coast and Nelson region, and its record of the earthquake is most valuable. Azimuth deductions from that record and from the one made at Christehurch very definitely place the epicentre of the earthquake some fifty miles or so out at sea, distinctly to the south-east of the area where the earthquake was felt most strongly. Azimuth deductions, however, are sometimes doubtful, but distance measurements made from the Wellington, Christehurch, Takaka, Hastings, and, other seismograph records all place the epicentre at approximately the same spot. Hence there is little doubt in the mind of seismologists where the earthquake originated. To those unacquainted with the vagaries of earthquakes it may seem somewhat curious that the worst effects of the earthquake were felt not near the epicentre, but over an area some distance from it. But such has been the case in many other earthquakes in New Zealand, in Japan, and elsewhere, and it is a phenomenon which seismologists cannot as yet explain. It can be and is theorised upon, but no satisfactory explanation has as yet been produced to account for it. When asked if the calculated epicentre of tho recent earthquake corresponded with any known centre of seismic activity, Dr. .'^dams said that it did not. But he added that in days when there were no seismographical instruments in the Dominion to make records of earthquakes with the accuracy achieved today, earthquakes, some of considerable violence, had occurred whose epicentre had been guessed to be "out at sea, about halfway between New Zealand and ths Chatham Islands." The real epicentre of these, suggested Dr. Adams, might have been closer to New Zealand than was supposed and might have corresponded with the epicentre of the recent earthquake. All the numerous reports of the earthquake received remark' upon the prolonged swinging motion felt. So pronounced was this swinging motion that in some instances it produced a feel ing of nausea akin to sea-si,ckness. Mr. A. W. Burrell, a trained observer at Stratford, records that an 801b pendulum swung 18 inches, and he also instanced that waves on a lily pond lapped on the north-west and southeast margins of the pond. This to the seismologist is somewhat curious, as although that may have been the direction of the earthquake, it is usually the transverse. waves which cause the damage, and the ripples on tho water might have been expected to take the' direction opposite- to that which they did. ■ . The -wide area over which the earth-quake-was felt^and the relative absence of jolting, coupled with the long swinging motion, point to the fact that the epicentre was very deep seated, perhaps ten miles below the surface. Tho science of seismology, however, has not yet reached such/a state of perfection that this can be dogmatised upon for certain. "-'s - r;; . ■