Australian sedimentary thickness from passive seismic methods

Output type: Exploring for the Future Extended Abstract

Short abstract: Australia's crust is blanketed by sedimentary cover. Knowledge of the distribution and thickness of sediments is crucial for assessing resource potential. Excellent constraints on sedimentary thickness can be obtained from borehole drilling or active seismic surveys, but these are expensive and often impractical in much of inland Australia. Recently, a relatively simple and low-cost method for estimating the sedimentary thickness using passive seismic data was developed and applied to seismic stations in South Australia. First-order estimates of the thickness of sediments are predicted from the delay time of the Ps converted phase generated at the sediment-basement interface via an empirical relationship constructed using borehole stratigraphy data. Here we expand the analysis to over 1500 seismic stations across Australia, covering numerous sedimentary basins that span the entire range of sedimentary basin ages from Precambrian to present-day. The new results clearly match the broad pattern of expected sedimentation based on the various Australian geological provinces. Using a new compilation of borehole data, we obtain a new, continent-wide empirical relationship from passive seismic delay to sediment cover thickness, offering a fast, simple and cheap way to characterise sediment thickness in under-explored areas. We apply the new relationship to the Exploring for the Future AusArray 2ºx2º data.

Citation: Marignier, A., Eakin, C.M., Hejrani, B., Agrawal, S. & Hassan, R., 2024. Australian sedimentary thickness from passive seismic methods. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts. Geoscience Australia, Canberra. https://doi.org/10.26186/149319