Landslides in the Sydney Basin - Geoscience Australia

Seismic Hazard in SydneyProceedings of the one day workshopFigure 1: Incised valleys of the Blue Mountains Plateau and locations mentioned in the text.Structure according to Bembrick et al. (1973).Landslide failure triggered by earthquakes has been widely reported internationally, especially intectonically active regions (e.g. Keefer, 1984; Keefer, 1994; Dadson et al., 2003). Despite beinglocated on a plate centre, earthquakes have been recorded in Australia, although events are of acomparatively lower frequency and lower magnitude than those at plate boundaries (Sinadinovski etal., 2000). McCue (1999) relates the distribution of earthquakes across Australia to the dominantnorth – south and east – west intraplate stress patterns (Figure 2) created through the northwardmovement of the Indo-Australian plate and the eastward movement of the Pacific plate. He showsthe development of north-west and north-east oriented shear zones across the Australian continent,aligned to areas of seismicity, uplift and earlier volcanism. The centre of Australia is dominated by anorth-west shear zone which extends from the east coast around Sydney. A north-east shear zoneoccurs parallel to the east coast and includes the south-eastern highlands. The Sydney Basin, and inparticular the southern end of the Blue Mountains Plateau which includes the Nattai River, isrevealed as an area of earthquake activity, the largest of which were recorded at Robertson in 1961and Burragorang in 1973 with magnitudes of 5.6 and 5.5 respectively (Drake, 1976; Reynolds,1976). The occurrence of earthquakes and intersection of shear zones across the Sydney Basin posesan important question. Could the landslides in the incised valleys of the Blue Mountains Plateau be101