Estimating interval velocities

A method of imaging a velocity structure of a subsurface region of the Earth, the method comprising:

• providing data comprising a data interval velocity of the subsurface and a data uncertainty associated therewith;
• determining an output grid onto which velocity profiles are to be estimated, and calculating a separation between each pair of desired grid locations;
• using said separation between locations to evaluate a correlation function, and using correlation values to form a covariance matrix that provides a model of a covariance between a velocity to be predicted in a prediction location on said output grid and said data interval velocity;
• providing a first, initial model based on said data comprising a first model interval velocity of the subsurface and a first model uncertainty associated therewith;
• performing a spatial prediction of the data interval velocity to form a second model comprising a predicted second model interval velocity of the subsurface and a second model uncertainty associated therewith, the predicted second model interval velocity being associated with the prediction location in the subsurface region,
• wherein the prediction is performed based on the first model interval velocity and the first model uncertainty, and based on the data interval velocity and the data uncertainty, and based on said covariance matrix;
• displaying a 2D or 3D spatial image of the velocity structure of the subsurface region from the second model.