A recording made using an apparatus called a seismograph; the analysis of its shock wave echoes detects the presence of rock layers that might contain pockets of petroleum or gas.
petroleum trap
Assemblage of porous rocks that contain recoverable oil reserves, which are produced from marine or land deposits.
shock wave
The shock wave spreads and sends back an echo, which varies with the density and depth of the layers of subsoil; with this information, the composition of the subsoil can be determined.
