1. The seismic trace from a source at A to a geophone at B is the same as from a source at B to a geophone at A if sources and receivers are similarly coupled to the Earth. More specifically, this is Scalar Reciprocity, applicable to pure-mode (e.g. P-wave) propagation only.
For converted waves, reciprocity requires interchanging the motion senses of the sources/receivers as well as their locations.; this is Vector Reciprocity. 
For split shear waves, Vector Reciprocity also applies. 
See also main page: Reciprocity_Theorem
2. The potential at a point M with respect to a current source at A is the same as if the points of measurement and source were reversed. Applied in electrical exploration.
- Thomsen, L., 1999. Converted-Wave Reflection Seismology over inhomogeneous, anisotropic media, GEOPHYSICS, 64(3), 678-690.
- Joe Dellinger and Bertram Nolte, (1997), "A crossed‐dipole reciprocity “paradox”," The Leading Edge 16: 1465-1471.