1. n. 
See: acquisition, amplitude variation with offset, common midpoint method, depth migration, dropout, fold, migration, offset, receiver, seismic record, seismogram, shot depth, spacing, spread, synthetic seismogram
2. n. 
Naturally occurring (static) electrical potential in the Earth. Spontaneous potentials are usually caused by charge separation in clay or other minerals, by the presence of a semipermeable interface impeding the diffusion of ions through the pore space of rocks, or by natural flow of a conducting fluid (salty water) through the rocks. Variations in SP can be measured in the field and in wellbores to determine variations of ionic concentration in pore fluids of rocks.
Alternate Form: spontaneous potential