Probabilistic seismic hazard analyses in Australia rely fundamentally on the assumption that earthquakes recorded in the past are indicative of where earthquakes will occur in the future. No attempt has yet been made to assess the potential contribution that data from active fault sources might make to the modelling process, despite successful incorporation of such data into United States and New Zealand hazard maps in recent years. In this paper we review the limited history of paleoseismological investigation in Australia and discuss the potential contribution of active fault source data towards improving our understanding of intraplate seismicity. The availability and suitability of Australian active fault source data for incorporation into future probabilistic hazard models is assessed, and appropriate methodologies for achieving this proposed.

GPR data have been collected across confirmed palaeofault scarps at Hyden and Dumbelyung, and also the scarp created by the 1968 Meckering earthquake. In each case there is a nearby trench to allow GPR responses to be related to known geology. At Meckering and Hyden, where the near-surface material contains moderate amounts of clay and the groundwater is fresh, it has proved possible to collect high quality data that images colluvium and also disrupted bedrock features which allow faults to be inferred. At Dumbelyung, where the near surface is more conductive due to clay-rich alluvial deposits and saline groundwater, results were poor and no sub-surface features were confidently identified. Our results demonstrate that, subject to the satisfaction of a predictable set of ground conditions, GPR surveys are a valuable tool for studying palaeofaults in deeply weathered terrains. The results provide sufficient information to confirm a topographic feature is of seismic origin, and to aid in siting trenches for palaeoseismic studies.

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The role of neotectonism in the recent landscape evolution of the Eastern Blue Mountains, NSW Dan Clark, Andrew McPherson and Kerrie Tomkins Faults of the Lapstone Structural Complex (LSC) underlie 100 km, and perhaps as much as 160 km, of the eastern range front of the Blue Mountains, west of Sydney. More than a dozen major faults and monoclinal flexures have been mapped along its extent. The Lapstone Monocline is the most prominent of the flexures, and accounts for more than three quarters of the deformation across the complex at its northern end. Opinion varies as to whether recent tectonism, erosional exhumation of a pre-existing structure, or a combination of both, best accounts for the deeply dissected Blue Mountains plateau that we see today. We present results from an ongoing investigation of Mountain Lagoon, a small fault-bound basin bordering the Kurrajong Fault in the northern part of the LSC. Drilling has identified 15 m of fluvial, colluvial and lacustrine sediments overlying shale bedrock trapped behind a sandstone fault barrier corresponding to the Kurrajong Fault. Dating of pollen grains preserved in the basal sediments overlying shale suggest that the fault angle depression began trapping sediment in the Early to Middle Miocene. Strongly heated Permo-Triassic gymnosperm pollen in the same strata provides circumstantial evidence that sediment accumulation postdates the emplacement of basalts at Green Scrub at ca. 18.8 Ma. Our results indicate that only 15 m of the 130 m of throw across the Kurrajong Fault is Neogene in age. From this it may be deduced that erosional exhumation is the dominant process responsible for formation of the deeply dissected Blue Mountains landscape. However, it is also possible to demonstrate the influence of ongoing tectonism on stream channel over-steepening, knick point initiation, and the continuing dissection of the plateau.

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