Simultaneous inversion of active and passive source datasets for 3-D seismic structure with application to Tasmania

Abstract

Refraction, wide-angle reflection and teleseismic arrival time data are combined in a simultaneous inversion for 3-D lithospheric P-wavespeed and Moho geometry beneath Tasmania, southeast Australia. A new iterative non-linear tomography scheme, which incorporates a novel grid-based method of traveltime prediction, is used to obtain the solution model. Synthetic resolution tests demonstrate that the crucial issue of trade-off between interface depth and layer velocity is satisfactorily resolved. In contrast to previous results from separate inversions of the active and passive source datasets, the new images reveal a zone of elevated wavespeed beneath the Cambrian Mt. Read Volcanics, and indicate that both crustal thinning and elevated wavespeeds occur beneath northeast Tasmania, which supports the case for the existence of a prior passive margin. Otherwise, most major inferences from the previous studies, including evidence for remnant subduction and crustal shortening, are supported by the new results.