One of the most common missteps we see in Adelaide is treating the entire metro area as having uniform seismic hazard. A site in the thick Quaternary alluvium of the River Torrens basin and another on the fractured Proterozoic bedrock of the Adelaide Hills face fundamentally different ground motions during a tremor. The 1954 Adelaide earthquake, though moderate at magnitude 5.5, caused localized damage patterns that still inform our baseline studies today. In our laboratory, seismic microzonation means integrating MASW profiling with borehole logs to define site classes per AS/NZS 1170.4, then mapping how the basin-edge effect amplifies shaking at specific periods. When a developer plans a multi-storey structure near the Para Fault escarpment, we correlate the soil profile with the bedrock depth model to avoid underestimating spectral acceleration. This work is not a desktop exercise; it requires direct field measurement of Vs30, careful sample logging, and a clear understanding of Adelaide's complex transition from sedimentary cover to hard rock.
A site class boundary can shift within 50 metres in Adelaide's foothills transition zone — mapping it correctly changes the design spectrum by a full site factor increment.
