Landslides in the Sydney Basin - Geoscience Australia

Seismic Hazard in SydneyProceedings of the one day workshopin the Sydney area since 1992 were under the Blue Mountains. Most events have been located to aprecision of a few kilometres or better, including depth. Although many near surface blasts and minecollapses have been recorded in coal mining areas, very few earthquakes appear in the top fewkilometres. It is possibly that the Mesozoic sediments of the Sydney Basin are too weak to sustainvery high stress. The deepest earthquakes that have been precisely determined are about 17 km deep.Figure 4: Vertical sections with earthquakes before 1992 (top) and 1992 to 1998 (bottom)Although the overall rate of earthquake activity for the region is not altered significantly by the newdata, a possible re-distribution is both reasonable in terms of geology and topography, and indicatesthat the Blue Mountains region has a higher level of earthquake hazard than the Sydney region.Although the level of activity under the Blue Mountains is above average by Australian standards, itis still far less than in the active earthquake areas of the world. The recording period is very short53