Crustal Heterogeneity and Moho Uplift in the Northern Gawler Craton from Trans-dimensional Bayesian Joint Inversion of Receiver Functions and Surface Wave Dispersion

Summary The buried Nawa Domain of the Gawler Craton, Australia, remains poorly understood, with its deep structure and connections to adjacent terranes largely unknown. We apply a trans-dimensional Bayesian joint inversion of receiver functions and surface wave dispersion along the Marla line, a dense passive seismic array that crosses the craton margin, to image a two-dimensional shear wave velocity profile across over 200 km distance and down to 60 km depth. Our model reveals two low-velocity anomalies: within the craton, where Vs is reduced by about 6 per cent, possibly from fault-related fracturing and elevated heat flow; and at the craton margin, where a 7 per cent low-velocity anomaly spans the crust and extends into the upper mantle, likely linked to the Norwest Fault and thick sediments. Moreover, an increased Vp/Vs ratio near the Norwest Fault, generally above the profile median and locally reaching high values of about 1.80–1.85, provides evidence for mantle-derived fluid migration. The Vs model also reveals Moho shallowing by 10-15 km toward the craton margin, from about 50 km beneath the craton interior to 35-40 km beneath the basin. Edge-driven convection caused by lithospheric steps may drive mantle migration along faults and Moho uplift.