EARTHQUAKE IN PROVINCE

Press, Volume LXXXII, Issue 24913, 28 June 1946, Page 8

EARTHQUAKE IN PROVINCE

CENTRE NEAR LAKE HERON

FAULT LINES IN REGION

“The earthquake shock which alarmed so many people at 12.36 a.m. to-day was, in my judgment, the worst felt locally since the Buller earthquake in June, 1929.” said Mr H. F. Baird, director of the Christchurch Magnetic Observatory, yesterday. “While it is not my desire to make people think they should not have been genuinely alarmed it is, however. necessary to point out that this shock was very much smaller than the dimensions of a major earthquake. “The instruments suggest that the origin was in the general region of Lake Heron, which is about 70 miles west of Christchurch. Accurately fixing the distance and direction of such an earthquake is beyond the capacity of our recorders alone; however, when the times of first arrival at various seismographs throughout New Zealand are collated at the Dominion Observatory, Wellington, a closer fixing of the actual origin will be available. Recorded for Only Two Hours “Records of large shocks, such as the Hawke’s Bay one of 1931. last about six hours and are widely felt throughout New Zealand. This one produced recorded movement for only two hours and was not felt much, even as near as Wellington. That it was felt strongly, too, at Dunedin favours an origin west of Christchurch. It must be remembered that Dunedin is almost as far west of Christchurch as it is south of it; therefore Lake Heron is nearer to Dunedin than is usually realised. Actually Mount Cook is about due west of Lyttelton. “Until recently fault lines near Lake Heron have been regarded as dormant, but until 1929 so were those near Murchison. A brief century of settlement and investigation by Europeans has once again proved—as naturally it must—inadequate for delineating our potential areas of seismic activity. Great Factor of Safety “That this origin was as much as 70 miles from Christchurch was a great factor of safety to this city, but, as geologists have already delineated other dormant faults at only half that distance away, cogent reason exists for adopting earthquake-resisting design in our own city. Since 1901 Christchurch has had fewer reminders of •this need than it had previously, but it has had reminders running to double figures in well under a century. “This earthquake was preceded by a foreshock some 21 minutes earlier, a felt aftershock came about 42 minutes later, and two smaller ones before 5 a.m. Such happenings are normal with an earthquake which is not deep seated and represent grounds for anticipating that this activity will gradually abate without serious repercussion of strong activity ” No Serious Damage

Recordings at the Christchurch Magnetic Observatory showed tremors of between five and six degrees on the Rossi-Forel scale and five on the modified Mercalli scale.

No reports of serious damage have been received from areas near the estimated centre of the disturbance, although residents of Lake Coleridge felt minor shocks throughout the early part of the morning and there was some interruption in telephone services.

In Christchurch, beyond dislodging some loose bricks and upsetting pendulum clocks, no serious effects of the tremors were reported yesterday. The only earthquake damage reported yesterday at Rangiora was a broken wireless aerial. Many residents reported feeling a smaller tremor about half an hour after the first shake. The only result of the severe earth tremor at Waimate was that the town clock stopped at 12.35 a.m.