Next-generation velocity model of the Australian crust from synchronous and asynchronous ambient noise imaging

The proliferation of seismic networks in Australia has laid the groundwork for improved probing of the continental crust. In this study, we develop a new crustal model of the Australian continent using a large dataset that consists of nearly 30 years (1992-2019) of continuous seismic recordings from over 1600 stations. This unprecedented dataset is further exploited with a recently developed ambient noise imaging workflow that enables integrating temporary seismic arrays deployed at different times. We compute two sets of noise correlation functions (NCFs) between 1) synchronous stations with the conventional ambient noise correlation (i.e., C1) and 2) asynchronous pairs with the high-order correlation technique (i.e., C2) based on correlational and convolutional types of source-receiver interferometry. The C2 approach enables extracting three times more NCFs than available from using C1 alone, leading to a dataset that is ten times larger than that utilized in the most recent model. The final 3D shear velocity model reveals fine-scale structures in the Australian crust. The low velocities at shallow depths (<10 km) are in excellent agreement with the distribution of known sedimentary basins. Our model also sheds new lights on the previously poorly constrained lower crustal and upper most mantle shear velocity structures. While the Moho depth derived from our model is generally consistent with that of the reference model (AusMoho), our model provides new information to central-south Australia where a large data gap exists in earlier seismic surveys. In conclusion, this study provides significantly improved constraints on the shear velocity structures and lays a new basis for developing the next-generation crustal model of the Australian continent.