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South West seismic zone

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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. ^ a b 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.

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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