Geophysical data from closely spaced ship tracks in the central Gulf of California delineate tectonic features associated with the Pacific–North America plate boundary.

Three en echelon fracture zones extend southeast from Delfín Basin through Salsipuedes Channel to the northern part of San Pedro Martir Basin, southwest from the southern part of San Pedro Martir Basin to the northeastern flank of Guaymas Basin, and southeast from Guaymas Basin. Large magnetic anomalies and abundant volcanism are associated with segments of these faults. The faults are interpreted to represent a transform fault zone here designated as the “Guaymas fault zone.”

Active spreading is taking place within the Guaymas and possibly the San Pedro Martir Basins, although patterns of sediment distribution within these basins preclude a model of simple stationary positions of active spreading centers for more than a few tens of thousands of years at a time.

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