The western margin of the Sierra Cucapa is defined by the Laguna Salada fault, a complex zone of active oblique-dextral slip faults. The northwestern section of the fault zone consists of a single fault strand which has had an oblique-dextral sense of slip throughout the late Pleistocene and Holocene. The southeastward continuation of this single fault strand has been comparatively inactive during the Holocene. Slip during the late Quaternary has instead been stepped several hundred meters to the southwest onto two distinct oblique-dextral fault strands. The easterly strand extends southeastward and intersects the Canon Rojo fault, a northwest-dipping normal fault which has been active throughout much of the late Quaternary.

This zone of normal slip and other northwest-dipping normal faults have transferred dextral slip from the Laguna Salada fault zone during the late Quaternary to several other oblique-dextral zones successively farther to the southwest. This connected series of northwest-striking oblique-dextral and northwest-dipping normal fault zones collectively forms a series of dilational right steps that are responsible for basin subsidence and pull-apart within Laguna Salada. Geomorphic evidence suggests that pull-apart was not continuous during this period and ceased at least once within the northern part of the Laguna Salada basin.