Australian Seismological Reference Model (AuSREM): crustal component

Although Australia has been the subject of a wide range of seismological studies, these have concentrated on specific features of the continent at crustal scales and on the broad scale features in the mantle. The Australian Seismological Reference Model (AuSREM) is designed to bring together the existing information, and provide a synthesis in the form of a 3-D model that can provide the basis for future refinement from more detailed studies. Extensive studies in the last few decades provide good coverage for much of the continent, and the crustal model builds on the various data sources to produce a representative model that captures the major features of the continental structure and provides a basis for a broad range of further studies. The model is grid based with a 0.5 degrees sampling in latitude and longitude, and is designed to be fully interpolable, so that properties can be extracted at any point. The crustal structure is built from five-layer representations of refraction and receiver function studies and tomographic information. The AuSREM crustal model is available at 1 km intervals. The crustal component makes use of prior compilations of sediment thicknesses, with cross checks against recent reflection profiling, and provides P and S wavespeed distributions through the crust. The primary information for P wavespeed comes from refraction profiles, for S wavespeed from receiver function studies. We are also able to use the results of ambient noise tomography to link the point observations into national coverage. Density values are derived using results from gravity interpretations with an empirical relation between P wavespeed and density. AuSREM is able to build on a new map of depth to Moho, which has been created using all available information including Moho picks from over 12 000 km of full crustal profiling across the continent. The crustal component of AuSREM provides a representative model that should be useful for modelling of seismic wave propagation and calculation of crustal corrections for tomography. Other applications include gravity studies and dynamic topography at the continental scale.