South of lat 28° N., the axis of the Gulf of California is associated with a gravity high of about 100 mgal Bouguer anomaly which falls off rapidly to about 0 mgal at the sides. This anomaly correlates closely with the deeper water and has been interpreted as a long, narrow strip of dense crust resembling an oceanic section, bordered on either side by a crust of continental type.

North of lat 28° N., this dominant axial high is replaced by a patchwork pattern of anomalies whose magnitude rarely exceeds ±20 mgal. The most pronounced features are a number of relatively restricted areas of low negative anomaly located on both sides of the Gulf and elongated parallel to its general direction. These areas probably mark elongated basins of thicker-than-normal sediment associated with faults, although there is little corroboratory evidence for this interpretation. One of these features, on the mainland side of the Gulf near its head, could mark an extension of the San Jacinto fault.