GSWA Open Day 2024 | Perth Basin and basement: new insights from deep-crustal reflection seismic

GSWA Open Day 2024 | The Perth Basin and
basement: new insights
from deep-crustal reflection
seismic profiles
Charmaine Thomas, Senior Geologist /
Geophysicist
In 2023, GSWA hired Hi-Seis to collect three seismic profiles in different areas: the Perth Basin, the Proterozoic Inliers of the Pinjarra Orogen, and the Yilgarn Craton. These profiles recorded 20 seconds of seismic data, which was processed to create clearer images of the underground structures. The processing included techniques called prestack time and depth migration.
While the Perth Basin already has a lot of seismic data from the petroleum industry, the new lines were placed in areas where data was less available or where older, shorter seismic lines existed.
One of the new lines, SW1, is the only seismic image of the Leeuwin Inlier and the Dunsborough Fault, which separates it from the Perth Basin. Line MW1 shows the layers of rock from the Devonian (and possibly older) to Permian periods, along with the Urella and Darling Faults, and how these rocks overlap with the Northampton Inlier. It also shows the Proterozoic metasedimentary rocks underneath. Line MW2 is the only seismic image of the Proterozoic Moora Basin, which helps explain the complex structure of the Coomallo Trough and Cadda Terrace areas in the Perth Basin.
In all three seismic lines, the Moho (the boundary between the Earth’s crust and mantle) is hard to detect beneath the basin and a narrow strip of the craton next to the Darling Fault. However, the Moho is usually easier to see in the craton area. Further analysis, including using other GSWA data such as passive seismic velocities, is continuing to help understand the large-scale processes that formed these basins.
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