Earthquakes Every Two Or Three Days

Press, Volume CIX, Issue 32073, 22 August 1969, Page 12

Earthquakes Every Two Or Three Days

A seismograph installed in the basement of the Canterbury Museum at the end of last month had already recorded a number of earthquakes, said Dr R. S. Duff, the museum’s director, yesterday.

Dr Duff told the Museum Trust Board that the- seismograph had recorded earthquakes every two or three days. There was one on August 3 at 12.30 p.m., one on| August 5 at 4.40 am., oneon August 8 at 1.38 a m. and! one on August 18 at 2.38 a.m. ■ The August 18 earthquake! was felt on the West Coast. On August 12 at 9.41 a.m.! an earthquake was recorded! and abnormal ground move-| ments continued for at least 74 minutes. Dr Duff said that the Seismological Observatory in Wellington, which installed the seismograph, had reported that these were the shock waves from a major earthquake in the Kuril Islands north of Japan. The museum’s seismograph Is part of a network of about 30 stations run by the Department of Scientific and Industrial Research, extending from Samoa to the Antarctic. “The seismograph will form part of a display on earth- j quakes under construction in the Von Haast Hall of Geology,” said Dr Duff. “A sensitive detector and timing equipment in the basement will be connected by electric! cable to a recorder on public view in the Geology Hall. I Temporarily the recorder is operating in the basement He said that the museum’s seismograph had to be run at a relatively low amplifica-

tion because the ground under Christchurch —unconsolidated sand and gravel—was in constant vibration. In addition, the ground vibration increased with the intensity of the wind, which presumably shook the building. But he reported that Mr R. D. Adams, superintendent of the Seismological Observatory, had said that the low amplification necessary in Christchurch was an advantage, because it enabled observation of the larger earthquakes, which often over- ! loaded more sensitive instruments.