Exemplary shot gathers (SPs 30 and 46) with seismic traces along receiver borehole and surface and first break picks indicated (dots). Trace numbers 1–133 and 1–140 have been recorded by borehole receivers (SP 30 and SP 46, respectively), from bottom to top, trace numbers 134–173 and 141–180 (SP 30 and SP 46) have been recorded by surface receivers, from left to right.