Because of deformation type differences in gas-oil reservoirs under pores saturation (> 90%) by liquids, only fast wave Р, is propagating but in gas layers this wave attenuates and only slow wave P
is observed. This fact explains a seismic shadow beneath of gas horizons for waves Р,. Positive results of low frequency seismic waves are explained by changes of P-waves types. Dominant frequencies of passive seismic and active (vibrate) action corresponds to different resonant wavelengths. The equation of own layer oscillations is derived that contains the intervals of negative damping for dominant frequencies. According observations and recommended equations random disturbances are strengthening the useful signals at dominant frequencies. Waves P
of dominant frequency at active action are penetrating into the shadow of wave Р
and give more detailed picture of rock saturation with oil. They are useful for AVO methods. Oil layer full with gas bubbles and compressed by depth rock pressure is oscillating as a whole body under external seismic action.......