3D Structure of Flinders Ranges from Local Earthquake Tomography

The Flinders Ranges, situated in the Adelaide Fold Belt, South Australia, lie within a region of relatively high active intra-plate deformation that manifests as a distinct concentration in seismic activity. Unlike most other stable continents, maximum horizontal compressive stress trajectories in the Australian crust do not align with absolute Australian Plate velocity, and have a particularly complicated configuration in the Flinders Ranges area. Although near surface structure has been exhaustively studied via geological mapping, geochemical analysis and potential field data, there is a consistent lack of deep seismic profiling or high resolution 3-D tomographic imaging that could impose important constraints on the broad scale geology of the crust. In this study, local earthquake tomography is carried out in the Flinders Ranges in order to simultaneously improve hypocenter locations and 3-D variations in velocity structure, with the goal of improving our understanding of crustal structure, rheology, and the mechanism responsible for the localized deformation. The data used for this purpose were traveltimes from approximately 500 local earthquakes, most of which are located above of 25 km depth and were recorded by a temporary network of 47 broadband seismometers. The solution model has been obtained via an iterative non-linear method which uses the fast marching method (FMM) for the forward step of traveltime prediction, the subspace method for velocity structure recovery, and the neighborhood algorithm for source relocation.