EARTHQUAKE AREA RECONNAISSANCE

Dominion, Volume 23, Issue 54, 27 November 1929, Page 10

EARTHQUAKE AREA RECONNAISSANCE

REPORT BY GEOLOGICAL EXPERTS

The Murchison earthquake of June 17, which it appears is still causing quite severe after-shocks, has been the subject of initial investigation by the Geological Department.

Mr. H. T. Ferrar and Sir. L. I. Grange, in a recent issue of the “New Zealand Journal of Science and Technology,” give some interesting facts concerning the matter. The Murchison earthquake, in which some 2000 cubic miles of solid granite and other rocks were raised from five to fourteen feet, seems to have broken quite a few of the accepted rules and regulations of these phenomena, it is stated. Long-dormant faults, for instance, have hitherto been accepted as of little danger. The Murchison earthquake, however, was generated along what is known as White Creek fault. This fault is at least seven miles long, and although apparently dormant, suddenly came to life and allowed an earth-block to rotate.

“The recorded uplift of 14 feet 9 inches,” states the report, “caused a block of country to tilt eastwards on the convex side of the fault." Moreover, the Murchison earthquake also seemed to differ in another respect from other earthquakes experienced In New Zealand, in that it was in the nature of a double earthquake with foci on two nearly. parallel lines of weakness, namely, the White Creek and the Konhahu fault zones.

“The result,” the report explains, “was that the north-west corner of the South Island continued to creak like the deck of a ship for weeks after the first disturbance took place. The after shocks, presumably similar to the one experienced only a few days ago, It is explained, are blessings in disguise, for they indicated that earth stresses were being released rather than accumulated. The longer they continued the less likelihood there was of a repetition of the first severe shake.”