Stable downward continuation of potential field data using an equivalent source method and a constrained strategy

Based on the principles of equivalent source method, the presented work proposes a constrained equivalent source for downward continuation of potential filed data, of which the constraint includes the data measured below the observation surface. The equivalent source constrained downward continuation method exhibits improved noise suppression and can capture high-frequency signals that are difficult to probe due to the increasing continuation depth, thus providing more realistic results compared with the conventional downward continuation method. The results of the continuation of synthetic gravity data demonstrate that this method is more accurate than traditional wave number domain iteration method and equivalent source method, evidencing its effectiveness. The downward continuation of the gravity data measured on the surface of a certain sea area in China agrees very well with the data measured underwater. The equivalent source constrained downward continuation method provides technical support for the research of high precision gravity and magnetic exploration of deep-water oil and gas near seabed in China.