On the left the predicted-to-observed ratios are compared.  The predictions were obtained using hard rock Green’s functions with QTM site corrections.  Circles, squares and triangles represent quaternary, tertiary and Mesozoic sites respectively.  Open symbols indicate under prediction and filled symbols indicate over prediction. The symbol size is scaled to the ratio.

On the right significant improvement is observed.  In this case both hard and soft rock Green’s functions were used to account for site variability.  LA Basin is still under predicted but much less so.  It is interesting that the “rock” sites around the basin remain significantly under predicted.  This may be due to unaccounted for regional structure effects, and may be improved using  numerically derived 3D corrections.