Source-receiver reciprocity and empirical Green's functions from chemical blasts

We investigated source-receiver reciprocity in the context of empirical Green's functions (EGF) for chemical blasts. Theoretically, reciprocity holds between a purely explosive source and the divergence of the displacement field (dilation). Using a pair of large, delay-sequence mining blasts in southern Indiana, we carried out a pilot experiment in the field. Preliminary results show that reliable EGF can be obtained using reciprocity below a frequency threshold of about 2 Hz, where fine details in the source function are not critical. These results have applications for the characterization of seismic sources and wave propagation at local and regional distances using reciprocal geometries.