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][3]

It was known earlier as the Yandanooka–Cape Riche Lineament,^[4] including the physiographic boundary known as the Meckering Line, and also the junction between Swanland^{[clarification needed]} and Salinaland^{[clarification needed]}.^[5][6]

The zone exists within an Archaean Shield structure called the Yilgarn Block.^[7] The identified geological subdivisions within this Precambrian structure do not show an obvious relation to the seismicity.^[8]

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.^[8] Meckering, Cadoux and Burakin earthquakes originated in the SWSZ. More recent events have occurred to the south in Lake Muir in 2018^{[9][10][11][12]} and Arthur River in 2022.^[13]

The zone and the explanation of it, has been titled Perthquake in the Catalyst programme on the ABC in 2001.^[14]

Temporal variation of the events in the region have been analysed over time.^[15][16] In the 2000s, monitoring and instrumentation was developed in the region.^[17][18]

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).^[19]