Seismic attenuation modelling for Melbourne based on SPAC-CAM procedure

A pilot study conducted in Melbourne involving shear wave velocity (SWV) profiling in the bedrock formation is used to illustrate a new approach for predicting the potential seismic attenuation characteristics for the region. A complete SWV profile for the entire seismogenic depth of the earth's crust is first developed by combining the SWV profiles measured by the Spatial Auto-Correlation (SPAC) method with regional information provided by a global crustal database. Secondly, the crustal amplification function calculated from the representative SWV profile is combined with predicted attenuation parameter values (kappa K and Q0) to form a complete filter. function representing the potential wave modification characteristics of the earth's crust in the area. Thirdly, a seismic attenuation model is developed by combining this filter function with the source function of the earthquake, using a stochastic procedure and the framework of the Component Attenuation Model (CAM). Lastly, the developed attenuation relationship is compared with seismic Intensity information obtained from three historical earthquakes that affected Melbourne and its surrounding region. The modelling described in this paper only deals with seismic ·wave modifications within the bedrock formation whilst modifications within the soil sedimentary layers are to be addressed in separate analyses.