AuSREM: Australian Seismological Reference Model

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. 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 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, and we are 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. 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 10 000 km of full crustal profiling across the continent. In the upper mantle, the primary source of information comes from seismic surface wave tomography and a representative model has been developed to capture the features of a range of studies. Body-wave studies and regional tomography provide useful constraints on the relationship between P and S wavespeeds. The mantle model extends beyond the continent and so covers a larger area than for the crust. Below 350 km and in the surrounding area, AuSREM is linked to the S40RTS model. Potential applications of the AuSREM model come through the delineation of major structural features in the crust and mantle, and consequent improvements in, for example, earthquake location within the continent and at the nearby plate boundaries.