Billeroy Feels Boorowa Tremor.
By Peter Cochrane
At 7.16pm on Friday night central west NSW experienced a 3.8 magnitude earthquake. The earth quake was felt as far away as Billeroy, over 40kms from the epicenter and at least 10km further than preliminary estimate placed the shake zone. Local residents George and Peter Cochrane have different accounts of the incident due to the different positions they were in. Peter Cochrane (who was sitting at the time) said he heard a long low rumble and saw a light shade and computer cords moving. George (who was walking at the time) only described the rumble. The differences are consistent with the old Mercalli Scale III and IV which use intensity or what people felt to describe the strength of an earthquake. The newer Richter Scale measures energy released by earthquakes.
Within ten minutes of the Earthquake, GeoScience Australia had a preliminary report online giving basic information on intensity , depth and position. The Quake’s epicenter was reported close to Frogmore near Boowora but the final report from Geoscience Australia suggests it was closer to Crowther.
Whilst Mainland Australia is unlikely to experience the catastrophic earth quakes of New Zealand, Asia and America, smaller earth quakes and tremors are not uncommon in Eastern Australia due to relatively complex rock structures which are still capable of small movements when the strain builds up. Recent tremors include another near Boorowa on 5th June and one 25km SE Yass on 16th June.
More Information on this Earthquake can be found at Geoscience Australia’s website www.ga.gov.au there is also a survey which can be filled in by anyone who felt the tremor.
EARTH TREMORS OVER LARGE AREA HITS GRENFELL - 1932
The earth tremor in the above article was not the only seismic event in the district to hit Grenfell. The following story covers a major tremor that struck the district in 1932. There was no major damage caused by that long-ago shaker although the severity was not able to measured immediately due to the lack of scientific expertise and sophisticated instruments available at that time. It goes to prove that earth moves to its own timetable. Also, change both above and below the Earth’s surface is inevitable and never-ending and is no different to what happens in the rest of the universe as our world hurtles through the void and circles the sun as it has done since the beginning of time.
It also goes to prove that, once again, Australia is the lucky country. We are all truly fortunate that our continent does not sit above moving tectonic plates that buckle underneath the earth from time causing untold misery and catastrophe in areas such as China, the Middle East, parts of America, Haiti and closer to home, New Zealand.
Peter Soley - Editor
OVER LARGE AREA.
No Damage Reported.
Two distinct earth tremors were experienced over a large area of the State shortly after noon yesterday and, from reports which have been received it Sydney, it is calculated that a slight movement of the earth’s surface occurred somewhere more than 100 miles from Sydney in a west-south- westerly direction. No damage was done.
The exact site of the occurrence has not yet been determined but is thought to have been centred in an irregular area approximately oval in shape extending from Goulburn to Coolamon In the south (approximately 180 miles) and to Canowindra in the west (ap- proximately 120 miles). At many places the shock was so great that residents were under the impression that a large object had struck their houses whilst at others windows were shaken violently and crockery was thrown from shelves. At Canowindra a heavy anvil swayed perceptibly. A slight shock was felt in several of the suburbs of Sydney
Accounts of the occurrence agree that there were two phases of the disturbance and that the first tremor was preceded by a low rumbling not unlike the sound of an explosion at a distance. The seismographs at Sydney and Riverview observatories recorded the shocks which scientifically were neither large nor important.
From Bathurst, Woodstock, Cowra, Canow- indra, Blayney, Millthorpe, Grenfell, Goulburn, Canberra, Coolamon, Boorowa, Ariah Park, Quandialla, Harden and Murrumburrah came reports of the phenomenon. In all cases the time given was between noon and 12.40 p.m. Riverview Observatory recorded it as 40 seconds after 12.40 p.m. Each tremor lasted only a few seconds and there was less than a minute’s interval between them.
PROFESSOR COTTON EXPLAINS
Professor Leo Cotton of the Department of Geology of Sydney University said last night that he had insufficient data upon which to form an opinion on yesterday’s occurrence. Practically all earthquakes and earth tremors however, were caused by a slipping of the earth’s crust along a line of fracture. On two previous occasions earth tremors had been experienced in New South Wales. One some years ago had been along the line of the Kurrajong and had revealed an important line of weakness. More recently there had been a disturbance along the coast between Newcastle and Kiama and was thought to have been due to a movement of the floor of the ocean about 20 miles from the coast. Father O’Leary of the Riverview Observatory said that slight movements of the earth’s crust had been fairly frequent in the past few months. As far as Australia was concerned there was absolutely no cause for alarm.