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, Western Australia.[6] More than six thousand earthquakes have occurred in the SWSZ in the years 1968 - 2002.[7] 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 [8]
Temporal variation of the events in the region have been analysed over time [9]
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).[10]
| 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 [11] | 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 |
Notes
- ↑ First named by H.A.Doyle (1971) Seismicity and Structure in Australia Royal Society of New Zealand Bulletin Vol.9 pp. 149-152
- ↑ M Leonard, D Darby, G Hu. (2007) GPS-geodetic monitoring of the South West Seismic Zone of Western Australia: progress after two observation epochs in 2002 and 2006( http://www.aees.org.au/Proceedings/Proceedings.html ) Intro: - 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.
- ↑ 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
- ↑ 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
- ↑ http://www.seismicity.see.uwa.edu.au/welcome/seismicity_of_western_australia#SW
- ↑ M Leonard, D Darby, G Hu. (2007): 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.
- ↑ http://www.seismicity.see.uwa.edu.au/welcome/seismicity_of_western_australia#SW
- ↑ http://www.abc.net.au/catalyst/stories/s392312.htm PerthQuake
- ↑ M.O. Michael-Leiba Temporal variation in seismicity of the Southwest Seismic Zone, Western Australia: implications for earthquake risk assessment Geoscience Australia
- ↑ 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
- ↑ Following start of Mundaring Observatory more precise times were recorded.
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
External links
- http://www.rsuw.daleh.id.au/html/latest_earthquakes.html - in the section lower in page Western Australia
- http://webmap.ga.gov.au/imf-natural_hazards/imf.jsp?site=natural_hazards_earthquake - identifies recent earthquakes in each state
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