b'Geophysics in the SurveysNewsGeological Survey of Western Australia: SWAN takes off - a new seismic monitoring project in Western AustraliaThe Geological Survey of Western Australia, in collaboration with the Australian National University, Macquarie University, the Department of Fire and Emergency Services and Geoscience Australia, has just installed the first seismometers of an array across the South West Seismic Zone of Western Australia. This region is one of the most seismically active areas of Australia having experienced over 2000 small (between M L2 to 3) earthquakes since the year 2000. Many smaller events are also noted by the local people who often hear them coming. Yeshear them comingthis area is known for its noisy earthquakes. Most of these earthquakes occur in swarms rather than main shock-aftershock sequences (Dent 2015). This means that the region experiences a lot of small earthquakes, all much the same size and which occurFigure 1.Photo of the railway line near Meckering after the 1968 earthquake.in a similar area. These swarms can be active for years.The hazard associated with these seismic events is relatively small. However, in the past six decades this region has also hosted five of the nine surface rupturing earthquakes in Australia, most notably; Meckering (M 6.5) in 1968 from which there are photos of the bends in the railway lines (Figure 1) and faulting of 2-3 m in height across the fields (Figure2) (Gordon and Lewis 1980; Johnston and White 2018; Clark and Edwards 2018); Calingiri (M5.9) in 1970 and Lake Muir (M5.6), which was felt by a lot of people across Western Australia just two years ago (Clark et al. 2020).Despite the high rates of seismicity, seismic monitoring in the region remains relatively sparse. To overcome this lack of instrumentation, the consortium of institutions mentioned above, cameFigure 2.Aerial photo of the surface rupture associated with the 1968 Meckering earthquake.together for an ARC Linkage project to put in place a temporary network- the South West Australia Networkmagnitude earthquakes that can be useddata has the potential to assist in the (SWAN) - to improve the monitoringto improve the crustal velocity modelsdevelopment of improved methods for and detection capabilities in this area.which in turn enables more accuratemodelling how shaking intensity varies This project will see a total of twenty- earthquake locations and helps theas it propagates through the earths crust five broadband seismometers deployedunderstanding of the crustal structurefrom the earthquake source.across the southwest of Westernof this part of Australia. Better velocity Australia for a period of approximately 2models also enable better magnitudeOverall, this information will feed into years (Figures3 and 4). calculation methods, which improvean improved understanding of the the knowledge about recurrence ofearthquake hazard in the Southwest This temporary array will enable theearthquakes of a certain magnitude.region of Western Australia. For detection and location of smaller- From a seismic hazard point of view, thislocal communities, it will provide OCTOBER 2020 PREVIEW 28'