Short note: 4D seismic time differences extracted from pre-stack seismic data

In time-lapse seismic studies, time difference is an important parameter in determining the distribution of oil and underground water because it provides information about reservoir velocity variation. In this short note, we describe a method to extract time differences from pre-stack seismic data based on the reflection time-distance equation. The time-lapse seismic vertical time differences calculated using this method are accurate and it is not necessary to know the interval velocity.