Five new seismic monitoring stations have been added to the Australian National Seismograph Network (ANSN) in Western Australia with the aim of better locating the small earthquakes of the Southwest Seismic Zone of southwest Western Australia. The Southwest Seismic Zone, one of the most seismically active onshore areas in Australia, is an area known for its seismicity by the local people who regularly experience small cupboard rattlers. These often occur in swarms as documented by Dent (e.g. 2009, 2014, 2017, 2019, 2020). It is more widely known for the M6.5 Meckering earthquake of 1968 which destroyed many houses in Meckering, produced a 37 km long and 2 m high fault scarp and dramatically bent the railway line. There is no obvious tectonic reason for PREVIEW AUGUST 2021 earthquakes to be occurring in this area as it is in the middle of an Archean cratonic region although the scarps from surface rupturing events, such as the Meckering event, mainly trend approximately north-south and appear to lie along trends in the magnetic data (Dentith et al 2009). Until mid-2020 the ANSN had a fairly sparse coverage of the area. A secondary Public Seismic Network (PSN) is also monitoring in the area. Inclusion of the PSN data has quite an effect on the calculated locations, as exampled by the tighter clustering of the Beacon swarm of 2009 (Dent, 2009) rather than the linear trend from just using the ANSN data. In mid-2020 four more semi-permanent stations were installed in the area and one in the Goldfields and added to the data streaming into the National Earthquake Alerts Centre (NEAC) and incorporated into the location algorithm. This presentation looks at seismicity of the area, the small swarms that have been detected since then and the relationship of the seismicity to the geology. Presented at the 2021 Australasian Exploration Geoscience Conference (AEGC)

A ground-motion dataset from moderate-to-large magnitude earthquakes is compiled for earthquakes occurring in Proterozoic and Archean terranes of the Australian continental crust. Data, which are predominantly weak-motion velocity recordings, are compiled from low-sample-rate continuous waveform buffers and segmented high-sample-rate data (where available) recorded by the Australian National Seismograph Network (ANSN). Additional data are retrieved from various temporary deployments and, more recently, from the Incorporated Research Institutions for Seismology (IRIS) data centre. All raw data were first converted to a uniform miniSEED format from various binary and ASCII formats used over time. Corresponding instrument metadata is compiled in the standard FDSN StationXML format. The dataset currently contains 1497 earthquake recordings from 164 earthquakes occurring between 1990 and 2019. The magnitudes of earthquakes within the dataset range from MW 2.5 to 6.1 with hypocentral distances up to 1500 km. The time-series data are consistently processed to correct for the instrument response and to reduce the effect of background noise. A range of engineering parameters are calculated in time and frequency domains using the USGS’s ground-motion processing software, “gmprocess”. Numerous near-source recordings exceed peak accelerations of 0.10 g and range up to 0.66 g, while the maximum peak velocity of the dataset exceeds 27 cm/s. In spite of the limited number of seismic stations located throughout the Australian continental landmass, the dataset compiled herein will improve characterisation of ground-motion attenuation in the region and will provide an excellent supplement to ground-motion datasets collected in analogue seismotectonic regions worldwide. Presented at the 2021 Seismological Society of America (SSA) Annual Meeting