"Was the Clark Shaft accident at the Olympic Dam mine preceded by a seismic event?"
A geophysicist who investigated earthquakes for the US Geological Survey for 22 years, says that the connection between mining and seismicity [earthquakes] is obscured in Australia, particularly the seismic hazard of the Olympic Dam mine.
In a communication [Memo] sent to various federal and state government ministers [and others] on Tuesday 22 May 2010, Seismologist Edward Cranswick discusses the 35-km-long, steeply dipping Mashers Fault which passes through the middle of the Olympic Dam ore body. A fault length which implies an earthquake of maximum about 7.
The same memo is available as a PDF: http://cranswick.net/Kalgoorlie/KalgoorlieEarthquakeOlympicDamMine.pdf
A further observation by Cranswick is that censoring of Australian lists of earthquakes and their corresponding source parameters, (i.e., time, location, depth, magnitude) has taken place.
"A plummeting ore skip in the main shaft [Clark Shaft] at Olympic Dam on 06 OCT 2009 was announced as reducing capacity at the mine to about 20 per cent for up to six months", says Seismologist Edward Cranswick.
"No information about the cause of the accident has been released. However, the main shaft is ~2 km north-northwest of the surface expression of the Mashers Fault which dips towards it.
Was the accident preceded by a seismic event?" asks Edward Cranswick.
BHP Billiton has proposed to dig the largest open pit mine on the Earth at Olympic Dam, 4.1 km long, 3.5 km wide, 1 km deep.
On 04 DEC 2009, I emailed you a pre-print of my paper that you kindly acknowledged in a letter to me dated 15 DEC 2009 in which you noted that one of your departments, Primary Industries and Resources (PIRSA), would have a representative at the AEES conference. Previously, on 07 AUG 2009, I had made a Public Submission to your office about earthquake hazard&risk in response to the ODXdEIS, Seismicity anticipated to be stimulated by BHP's proposed open-pit mine at Olympic Dam .
"In Australia, rockbursting was first experienced as a significant but relatively infrequent problem in the Kalgoorlie district in the early part of the last [20th] century.
During the last decade of the century [1990s], as the extraction of the deepest massive orebodies of the Mount Charlotte mine peaked, several very large mining-induced tremors were experienced. Six seismic events between ML 2.5 and ML 4.3 (Richter scale) were recorded".
Bores in the 100-500-m-wide Mashers Fault zone near the mine have high fluid flows (ODXdEIS), and Ito and Zoback (2000)  find that, "critically-stressed faults in the crust are also the most permeable faults"; hence, Mashers Fault may be critically stressed. More recently at Olympic Dam, "damage from a plummeting ore skip in its main shaft [06 OCT 2009] is expected to reduce capacity to about 20 per cent for up to six months" (The Australian 21OCT2009) , but no information about the cause of the accident has been released - the main shaft is ~2 km north-northwest of the surface expression of the Mashers Fault which dips towards it. Was the accident preceded by a seismic event?
No decision should be made concerning the ODXdEIS until specific new investigations are undertaken at Olympic Dam and published -made available to the public - regarding the seismic hazard of proposed open-pit and the seismotectonic potential of the Mashers Fault.
These investigations of the Mashers Fault and vicinity would be conducted by independent teams that each focused on one of the following tasks: paleoseismology, i.e., evidence of previous fault movement; a microearthquake survey done in conjunction with the existing mine-wide microseismic monitoring system; a search of regional & national seismograph network data to recover all records of seismic events near mines (within 30 km), identification of sources, i.e., blasts or earthquakes, confirmed by mine blasting records; geomechanical analysis of in situ stress, pore pressure, borehole data, etc., to estimate Coulomb stress change (King et al. 1994)  on the Mashers Fault in response to excavation of the open-pit; geophysical analysis of gravity & magnetics to determine regional structure related to Mashers Fault.
An independent group of mining geologists, geomechanical engineers and mining seismologists would integrate the reports from the teams and write an overview, but all reports would be released in full as appendices. Much of this work has undoubtedly already been done - it needs to be released to the public and made available from a SA government website.
The majority of Australia's foreign exchange comes from mining, and mining is already the most hazardous industry in Australia . As mining activity increases, seismic activity increases, and the amount of toxic tailings from the mines that must be safely contained increases - both seismic hazard & risk increase. Following the recent example, "U.S. to Split Up Agency Policing the Oil Industry" (New York Times 11MAY2010) , the responsibilities to promote and to regulate mining, both now done by the one South Australian government department, PIRSA, should be divided between two independent departments.
Edward Cranswick 12 Bowillia Ave Hawthorn, SA 5062, TEL: 08 8271 1309 email: firstname.lastname@example.org
3. Hudyma, M., D. Heal, and P. Mikula (2003). Seismic monitoring in mines â€“ old technology â€“ new Applications, Proceedings of 1st Australasian Ground Control in Mining Conference, UNSW/EAGCG, Sydney, Australia, Nov, ISBN 0 7334 2085.
6. Cranswick, E. (2009). Mashers Fault and the seismicity anticipated to be stimulated by the proposed open-pit mine at Olympic Dam, in Kevin McCue and Sonja Lenz (eds.), Earthquake engineering in Australia: proceedings of the conference held by the Australian Earthquake Engineering Society in Newcastle, NSW, 11-13 December 2009. http://cranswick.net/MashersSeismicityAnticipatedOlympicDam/
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