Joint Inversion of Receiver Functions and Surface Waves from Ambient Noise and Earthquake Data: Australian Crust

We present the results from the joint inversion of radial receiver functions and group and phase velocities of Rayleigh waves for Australian crust. The receiver functions are calculated from the teleseismic earthquakes recorded at 24 broad-band stations of Tasmal experiment, which ran between 2003 and 2005 in central and eastern Australia with the aim of delineating the transition from Precambrian crust to Phanerozoic crust. The group velocities are derived from the continent wide tomographic images from the inversion of ambient noise Green's functions between the periods of 5 s and 12.5 s. The phase velocities are extracted from the continent wide tomographic images from the inversion of teleseismic earthquakes for the periods ranging from 40 s to 150 s. The joint inversion scheme employed in our analyses is a multi step procedure involving an initial grid search based inversion for estimating the simple crustal model and then an iterative inversion for constraining the finer structure. The combination of three different datasets offers a better constraint on the estimates of the crustal structure. We perform a sensitivity analysis on the different data sets by randomly excluding segments of the data from the joint inversion, and examining how the resulting crustal models vary. The estimated crustal thicknesses indicate the presence of the major geological blocks in the study area, e.g., Mt. Isa Block (north-east Australia) with relatively shallow crustal thicknesses, Gawler Craton (South Australia) with deeper crustal thicknesses, Thomson Orogen (east Australia) with shallow thicknesses in the central part and deeper values in the eastern segment. In addition to this, thick sediments located under the stations are revealed. The general trend of the crustal thicknesses, however, does not indicate a consistent transition from Precambrian to Phanerozoic Australian crust.