UNSTABLE EARTH

Ellesmere Guardian, Volume LII, Issue 32, 21 April 1931, Page 6

UNSTABLE EARTH

PREDICTION OF QUAKES.

SO MUCH "MOONSHINE."

An earthquake produced three dif- j ferent kinds of "waves," said Dr. P. ! Marshall, Government petrologist, in an address on "Earthquakes" deliver - |ed at the Wellington Rotary Club. j There was the compressional wave, | I which he compared with a row of billiard balls, which, if struck on one end, caused the ball at the other end to move; then there was the long waves and the short waves. The severity of the Napier earthquake was due to surface unlulations. We were on an unstable earth, which was gradually getting smaller, and the earth's crust had to adapt itself, said Dr. Marshall. It was when these stresses were of great magnitude that earth moved. Dr. Marshall produced a section of a fence post, brought from Hawke's Bay. This showed how the upheaval had caused the wire to break away from the staple, leaving marks on the wood, which gave some idea of the movements of the earth. It evidently moved backwards and forwards as well as up and down. From the evidence of the coastline it was fully 100 years since a similar earthquake affected the Napier area, and while they could not prophesy earthquakes, he did not think there would be another severe shock there for many years to come. That was supported by geological investigations. ''Earthquake prediction is absolute rubbish; moonshine is the most complimentary word one can apply to it" Dr. Marshall concluded. '"We have not sufficient knowledge to form any idea as to when a severe earthquake is likely to occur." There were two things wanted: knowledge of the tension and of how much stress the earth's crust could stand. Knowing neither of these things, earthquakes could not be predicted.