SECOND 



| G 



•*v --.,... ;': <»..■ ;:■ -A--:-'- «.'••■;. ,'.' ' ' skiff.' u V \r 



■-■ ■y^Z-h i .-:^y : j^^0, , ■ :;ff|vki^. v . . , : 

 ^a"''.< H':° ••.' • ' . • •• ■- ^m-f. ' - 'M'-O^fe-- J^" J ~- 



^ ?>■,..< ' • ■-■ :<-.-. •. -- £\? .• . ..-. f fV'T- fri z 7 : : ~^- rz . 



Figure 26-1. An actual seismic record (seismogram) and a schematic diagram of the simple 

 subsurface section from which it might have been taken. A — Timing lines recorded at 

 the rate of 100 per second allowing event timing to one millisecond, B — Galvanometer 

 traces representing ground motion, C — Arrival time of energy from shot to the top of 

 the shot hole or uphole time, D — Time of detonation or "time break," E — First arrivals 

 of energy, usually refracted events, F — Reflected events or reflections, G — Recording 

 truck, H — Shot, I — Seismometers, J — Reflected wave paths, K — Reflecting horizons, 

 L — Refracted wave paths, LVL — Low velocity layer. (After "Careers in Exploration 

 Geophysics," Society of Exploration Geophysicists) 



557 



