noise reduction method - offset vertical seismic profile
- oblique-slip fault
- oblique-slip normal dip fault
- obliquely bedded rocks
- obliquely incident ray
- obliquity
- obliterated waterfall
- obliteration of lakes
- oblong pillar
- oblong well
- obolus sandstone
- obovate
- obovoid
- obpyramidal
- obrotund
- Obruchev
- obruchevite
- OBS
- OBS data
- OBS operations
- OBS receiver
- OBS technique
- OBS technology
- obscure anomaly
- obscure bedding
- obsequent
- obsequent fault line
- obsequent fault-line scarp
- obsequent river
- obsequent stream
- obsequent valley
- observable (visible) anomaly
- observable anomaly
- observation
- observation line
- observation location
- observation point
- observation site
- observation site elevation finding
- observation site location finding
- observation station