INVERSION OF TRAVEL TIMES

In a vertically heterogeneous medium in which velocity increases with depth, the delay time function and, consequently, the distance and travel time functions are related linearly to depth as a function of slowness. Since all travel time inversions using surface measurements of travel time and distance require the removal of the effects of low velocity zones, we may assume this linearity always holds. The highly developed theory of linear inversion is thus applicable to the inverse travel time problem. Copyright 1979 by the American Geophysical Union.