Figure 3. Analysis of the travel time anomalies within a VAMP includes (A) identification of key horizons (arrows along right margin),

(B) derivation of velocity structure based upon interval time variation between picked horizons

and (C) interpretation of the anomalies in terms of equivalent volume of hydrate and gas within the section. Background velocity in the upper section is taken as constant at 1600 m/s. In this example, free gas content is <2% everywhere, and maximum hydrate concentration implied is ~20% of pore space. If the profile is a slice through the midpoint of a structure of cylindrical geometry, the hydrate zone alone contains ~0.87 Tcf of natural gas.