South West Seismic Zone

The South West Seismic Zone (also identified as SWSZ) is a major intraplate earthquake province located in the south west of Western Australia.[1][2] It was known earlier as the Yandanooka – Cape Riche Lineament, corresponds to the physiographic boundary known as the Meckering Line, and also the junction between Swanland and Salinaland.[3]

The zone exists within an Archaean Shield structure called the Yilgarn Block.[4] The identified geological subdivisions within this Precambrian structure do not show an obvious relation to the seismicity.[5]

The zone represents a significant seismic hazard to Perth.[2] More than six thousand earthquakes have occurred in the SWSZ in the years 1968 – 2002.[6] Meckering, Cadoux and Burakin earthquakes originated in the SWSZ.

The zone and the explanation of it, has been titled Perthquake in the Catalyst programme on the ABC in 2001.[7]

Temporal variation of the events in the region have been analysed over time.[8]

Table of earthquakes

List of earthquakes of magnitude 4 or more in Southwestern Australia 1920–1961 (based in part on the records of Perth Observatory 1923–1959 and Mundaring Geophysical Observatory 1959–1980).[9]

Date Origin time Epicentre
(lat., S)		 Epicentre
(long., E)		 Local magnitude Location
8 February 1920 05:24 35.00 111.00 6.2 260 km south west of Cape Leeuwin
18 December 1940 21:45 32.20 117.20 4.2 Beverley, Brookton
19 April 1946 21:13 38.5 114.5 5.7 West of Yallingup
17 September 1946 15:12 32.5 116.9 4.5 Pingelly
2 May 1949 10:00 30.90 116.40 5.1 Yerecoin
7 May 1949 17:09 30.90 116.40 4.1 Yerecoin
11 March 1952 06:09 31.30 116.50 5.1 Bolgart
27 November 1954 08:36 32.00 116.7 3.9 Talbot Brook
29 April 1955 09:14 30.90 116.40 4.7 Yerecoin
29 April 1955 19:49 30.90 116.40 4.4 Yerecoin
29 August 1955 06:09 30.70 116.40 5.3 Gabalong
30 August 1955 13:52 30.70 116.40 5.8 Gabalong
30 August 1955 14:07 30.70 116.40 4.7 Gabalong
30 August 1955 16:46 30.70 116.40 4.6 Gabalong
24 February 1956 06:27 30.9 116.4 4.5 Yerecoin
5 April 1956 23:13 30.9 116.4 4.5 Yerecoin
20 March 1958 03:03 32.20 117.20 4.8 Beverley, Brookton
3 October 1959 12:07:22.0[10] 34.50 114.50 4.2 55 km SW Cape Leeuwin
12 June 1961 18.00:51.0 34.20 114.50 4.1 50 km SW Cape Leeuwin
16 September 2018 5.7 Lake Muir[11]
13 October 2018 4.7 Lake Muir[12]
9 November 2018 5.07am (local) 34.423 116.787 5.4 Lake Muir[13] at a depth of 3 km (1.9 mi)[14]

Notes
  1. First named by H.A.Doyle (1971) Seismicity and Structure in Australia Royal Society of New Zealand Bulletin Vol.9 pp. 149–152
  2. Leonard, M; Darby, D; Hu, G (2007). GPS-geodetic monitoring of the South West Seismic Zone of Western Australia: progress after two observation epochs in 2002 and 2006 (PDF). Australian Earthquake Engineering Society 2007, Wollongong. Archived (PDF) from the original on 20 July 2008. Retrieved 2 June 2019. The Australian southwest seismic zone (SWSZ) is a north-south trending belt of intra-plate earthquake activity that occurs in the southwest of Western Australia, bounded by 30.5°S to 32.5°S and 115.5°E to 118°E. This is one of the most seismically active areas in Australia, with nine earthquakes over magnitude 5.0 occurring between 1968 and 2002; the largest of these was the M6.8 Meckering earthquake in 1968. Since the SWSZ lies as close as ~150 km from the ~1.4 million population of the Perth region, it poses a distinct seismic hazard.
  3. Geological Survey of Western Australia (1975), The Geology of Western Australia, Western Australia Geological Survey, ISBN 978-0-7244-6084-7 – section Southwestern Province by I.R. Williams page 65
  4. Geological Survey of Western Australia (1975), The Geology of Western Australia, Western Australia Geological Survey, ISBN 978-0-7244-6084-7 – section Yilgarn Block by I.R. Williams pages 33–81 – now called Yilgarn Craton
  5. http://www.seismicity.see.uwa.edu.au/welcome/seismicity_of_western_australia#SW
  6. http://www.seismicity.see.uwa.edu.au/welcome/seismicity_of_western_australia#SW
  7. http://www.abc.net.au/catalyst/stories/s392312.htm PerthQuake
  8. M.O. Michael-Leiba Temporal variation in seismicity of the Southwest Seismic Zone, Western Australia: implications for earthquake risk assessment, Geoscience Australia
  9. Gordon, F.R and J.D. Lewis (1980) The Meckering and Calingiri earthquakes October 1968 and March 1970 Geological Survey of Western Australia Bulletin 126 ISBN 0-7244-8082-X – Appendix 1 – Catalogue of Larger earthquakes recorded in Southwestern Australia – Table 22. Earthquakes of Magnitude 4 or more -page 213
  10. Following start of Mundaring Observatory more precise times were recorded.
  11. "Magnitude-5.7 earthquake rocks southern WA". Australian Broadcasting Corporation. 17 September 2018. Retrieved 9 November 2018.
  12. "Magnitude-4.7 earthquake rocks area surrounding Lake Muir in WA's Great Southern". Australian Broadcasting Corporation. 13 October 2018. Retrieved 9 November 2018.
  13. Ben Anderson (9 November 2018). "Earthquake at Lake Muir shakes Perth and WA's South West". News Corporation. Retrieved 9 November 2018.
  14. "Recent Earthquakes Lake Muir area,WA". Geoscience Australia. Retrieved 12 November 2018.
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See also

References
  • Featherstone, Will (1998) Geodetic monitoring of the South West Seismic Zone paper at Curtin University of Technology 24 25 September 1998 to the Advances in Deformation Monitoring International Workshop
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