# Translations:Synthetic seismogram without multiples/2/en

The time unit on a seismic trace is the time spacing of the sampling — for example, one time unit could be equal to 4 ms. This time unit sets the resolution of the seismic model in terms of the layering. In other words, the thinnest layer that can be distinguished has a two-way traveltime of 4 ms. Thus, the thickness of each layer is chosen so that the two-way traveltime (downward traveltime plus upward traveltime) in each layer is equal to one time unit. Each interface separating two adjacent layers with different impedances has a nonzero reflection coefficient. Of course, several thin layers can be lumped together to form a thicker uniform layer by setting the intermediate reflection coefficients equal to zero. The greater the impedance contrast is between the two adjacent layers, the greater is the magnitude of the reflection coefficient. For computation, the wave motion is digitized so that a signal becomes a discrete sequence (that is, a time series with discrete values separated by the given unit time interval).