ac5ee76f-a16a-4e5e-8e89-a75276377d11 urn:uuid eng UTF-8 nonGeographicDataset nonGeographicDataset 2025-10-16T16:05:40 creation ISO 19115 2016 Explosion seismic profiles, and implications for crustal evolution, in southeastern Australia ac5ee76f-a16a-4e5e-8e89-a75276377d11 The interpreted velocity-depth structure in the crust of the Lachlan Fold Belt in southeastern Australia indicates that velocity gradients, rather than discontinuous velocity changes, characterise the region. The velocity-depth morphology varies across the region. In the upper crust at depths less than 12 km, there is evidence in three areas for velocity decreases within a general velocity increase from about 5.6 km/s to 6.3 km/s. In the middle crust (depth range 16 km to about 35 km) a low velocity zone is interpreted within a general increase in velocity from 6.3 km/s to greater than 7 km/s; the prominence of the low velocity zone varies throughout the region. The upper mantle velocity is in the range 8.02 to 8.05 km/s; this velocity is reached at a depth slightly greater than 50 km under the highest topography in Australia, and at depths between 40 and 50 km elsewhere. There are similarities between the velocity-depth structure in southeastern Australia and that in the Appalachian Orogen of North America. Geochemical mixing and/or compositional inhomogeneity is a likely reason for the velocity-depth structures, and such inhomogeneity is probably still influencing current moderate earthquake activity and continuing highland uplift. In pre-Ordovician times the region of the Lachlan Fold Belt probably consisted of continental crust which was submerged and thickened by episodic crustal development similar to the processes which resulted in the Appalachian Orogen. {"type": "Polygon", "coordinates": [[[146.0, -37.0], [152.0, -37.0], [152.0, -32.0], [146.0, -32.0], [146.0, -37.0]]]} 146.0 152.0 -37.0 -32.0 Earth Sciences GA Publication Journal NSW Published_External VIC Journal article (pdf) documentDigital Journal article (pdf) PDF Unnamed resource documentDigital HTML