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, includes the physiographic boundary known as the Meckering Line, and also the junction between Swanland[ clarification needed ] and Salinaland[ clarification needed ]. [3]

Contents

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. [5] Meckering, Cadoux and Burakin earthquakes originated in the SWSZ. More recent events have occurred to the south in Lake Muir in 2018 [6] [7] [8] [9] and Arthur River in 2022. [10]

The zone and the explanation of it, has been titled Perthquake in the Catalyst programme on the ABC in 2001. [11]

Temporal variation of the events in the region have been analysed over time. [12] [13] In the 2000s, monitoring and instrumentation was developed in the region. [14] [15]

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). [16]

DateOrigin timeEpicentre
(lat., S)
Epicentre
(long., E)
Local magnitudeLocation
8 February 192005:2435.00111.006.2260 km south west of Cape Leeuwin
18 December 194021:4532.20117.204.2 Beverley, Brookton
19 April 194621:1338.5114.55.7West of Yallingup
17 September 194615:1232.5116.94.5 Pingelly
2 May 194910:0030.90116.405.1 Yerecoin
7 May 194917:0930.90116.404.1Yerecoin
11 March 195206:0931.30116.505.1 Bolgart
27 November 195408:3632.00116.73.9Talbot Brook
29 April 195509:1430.90116.404.7Yerecoin
29 April 195519:4930.90116.404.4Yerecoin
29 August 195506:0930.70116.405.3Gabalong
30 August 195513:5230.70116.405.8Gabalong
30 August 195514:0730.70116.404.7Gabalong
30 August 195516:4630.70116.404.6Gabalong
24 February 195606:2730.9116.44.5Yerecoin
5 April 195623:1330.9116.44.5Yerecoin
20 March 195803:0332.20117.204.8Beverley, Brookton
3 October 195912:07:22.0 [17] 34.50114.504.255 km SW Cape Leeuwin
12 June 196118.00:51.034.20114.504.150 km SW Cape Leeuwin

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. 1 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. 1 2 "School of Earth Sciences | Science".
  6. "Magnitude-5.7 earthquake rocks southern WA". Australian Broadcasting Corporation. 17 September 2018. Retrieved 9 November 2018.
  7. "Magnitude-4.7 earthquake rocks area surrounding Lake Muir in WA's Great Southern". Australian Broadcasting Corporation. 13 October 2018. Retrieved 9 November 2018.
  8. Ben Anderson (9 November 2018). "Earthquake at Lake Muir shakes Perth and WA's South West". News Corporation . Retrieved 9 November 2018.
  9. "Recent Earthquakes Lake Muir area,WA". Geoscience Australia . Retrieved 12 November 2018.
  10. "Earthquake 'swarm' rattles WA's south with more than 40 over three weeks". ABC News. 24 January 2022. Retrieved 25 January 2022.
  11. http://www.abc.net.au/catalyst/stories/s392312.htm PerthQuake
  12. M.O. Michael-Leiba Temporal variation in seismicity of the Southwest Seismic Zone, Western Australia: implications for earthquake risk assessment, Geoscience Australia
  13. Geological Society of Australia. Specialist Group on Solid-Earth Geophysics (3 June 1996), "Crustal Structure In The Southwest Yilgarn Craton, Western Australia – An Explanation For The Southwest Seismic Zone? (3 June 1996)", Geophysics Down Under: Newsletter of the Specialist Group on Solid-Earth Geophysics, Geological Society of Australia. Specialist Group on Solid-Earth Geophysics (23): 4, ISSN   1035-0853
  14. Dent, Victor; Harris, P; Hardy, D (2010), A new seismograph network in the southwest seismic zone of Western Australia, Australian Earthquake Engineering Society, ISBN   978-0-9807420-2-2
  15. Reading, AM; Kennett, BLN; Dentith, MC (2003), "Seismic structure of the Yilgarn Craton, Western Australia", Australian Journal of Earth Sciences, 50 (3): 427, Bibcode:2003AuJES..50..427R, doi:10.1046/j.1440-0952.2003.01000.x, S2CID   10466512 , retrieved 30 October 2021
  16. 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
  17. Following start of Mundaring Observatory more precise times were recorded.

See also

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References