1. A method of deleting and rescanning areas of a horizon display on a computer monitor, where a horizon is a topographic representation of a subterranean strata derived from picked points of a 3-D seismic data base, the method comprising the steps of: directing a cursor of a pointing device to a first area of said horizon display adjacent a second area of said horizon display, which is to be deleted, said first area covering at least a portion of an area of said horizon display with picked points; defining a first set of coordinates for said first area by activating a control button on said pointing device; defining a second set of coordinates for said second area by dragging said cursor of said pointing device from said first area to and across said second area, said first area being contiguous with said second area to form a combined area; deleting all horizon points within said second area defined by said second set of coordinates; scanning all points in said first area and designating all points picked in said first area as seed points; using said seed points to pick horizon points in said combined area; and filling in said combined area of said horizon display with said picked horizon points from said combined area.