FIELD OBSERVATIONS

Wairarapa Times-Age, 6 July 1942, Page 2

FIELD OBSERVATIONS

RECENT WAIRARAPA QUAKE MAJOR SEISMIC EVENT. DECREASE IN AFTER SHOCKS. (By Telegraph—Press Association.) WELLINGTON, This Day. Reporting on his field observations the acting-director of the Dominion Observatory, Mr R. C. Hayes, states that in locating the centre of the recent earthquake, valuable information was obtained by observing the direction of fall of objects overthrown by the earthquake. For instance, in the vicinity of Eketahuna, objects had fallen mostly toward the north-east, while near Carterton the predominating direction was about south-east. He explains that except very near the epicentre of an earthquake, objects will generally be overturned by the shear, or S-waves, in which the oscillations are at right angles to the wave-path. As usual in large seismic disturbances, aftershocks were frequent at first, but decreased rapidly in frequency and intensity. Up to July 1, there were 427 aftershocks recorded on the sensitive seimographs at Wellington. At the present time only a few small ones are being recorded daily. The main shock was felt from Auckland to Dunedin and Queenstown, the latter being 470 miles from the epicentre. This was practically the same as the limits of the Buller earthquake of 1929 and the Hawke’s Bay earthquake in 1931.

While the Wairarapa earthquake was undoubtedly a major seismic event, Mr Hayes says, the maximum intensity on the Rossi-Forel scale could be fixed tentatively at between 9 and 10. In many large earthquakes occurring at night, flashes of light similar to those recently reported were observed, but it would be difficult to distinguish any luminous phenomena of natural origin from those due to the shortcircuiting of power lines.