A 5.4 earthquake recorded by Geoscience Australia, SE of Moe in Victoria’s North on Tuesday night 19 June has already registered over 40 aftershocks up to Wednesday 20th June. The quake located within close proximity to the open cut coal mine at Morwell and Yallourn was felt in the centre of Melbourne and in suburbs across the city’s west and south-east.
Senior Seismologist and earthquake investigator Edward Cranswick, formerly of the United States Government Survey (USGS) has sent a reminder to media that an earthquake event occurring within 30 kilometres of an operating mine is considered by seismic experts to be mine induced.
In a memo FROM: Edward Cranswick, TO: The Hon Paul Holloway MLC, Government of South Australia, Federal Environment Minister Peter Garrett, and others in relation to mining induced earthquake findings after the Kalgoorlie Earthquake and in addition, the potential for earthquakes at the Olympic Dam Mine in South Australia, the former USGS investigator Edward Cranswick says:
There are reports from other stable continental regions of earthquakes triggered/induced by mines or other human activities (trigger: the fault is already near the breaking point and needs only a small stress change to fail). In the the Kaap-Vaal craton in South Africa, only 8 of the 378 magnitude 3.5-4 earthquakes recorded in 50 years were “natural” i.e., more than 30 km away from mining activity (Otlepp 2005); hence, 98% were near mines. In northeastern United States, one third of the earthquakes greater than magnitude 3 during the period 1971-2003 were “human triggered”, mostly by quarries or fluid injection (Seeber et al. 2004) .
By contrast, the Australian story seems to be that earthquakes can happen anywhere in Australia except at mines, and when they do happen at mines, it’s just coincidence – notable exceptions to this story are seismological papers about mining-induced seismicity, e.g., McKavanagh et al. (1995)  and Gibson and Peck (2006) .
Categories: GENERAL News