<p>This study examines the structural characteristics of the Cerro Prieto and Indiviso Faults within the Colorado River Delta, Baja California, México, through seismic reflection, seismicity, magnetic, and gravimetric analyses. The Cerro Prieto Transform Fault, a critical component of the Pacific-North American plate boundary, traverses the Mexicali Valley and northern Gulf of California, within the study area. A key objective is to determine whether the Indiviso Fault existed prior to or originated during the 2010 Mw 7.2 El Mayor–Cucapah earthquake. Results confirm the Indiviso Fault as a pre-existing structure reactivated during the event. Gravimetric and magnetic anomalies and seismicity delineate their obliquity to the Cerro Prieto Fault and intersection with the Wagner Basin, challenging prior models of the Cerro Prieto Fault's trajectory. Tectonic activity along the La Mesa and Santa Clara Faults correlates with significant subsidence beneath the Ciénega de Santa Clara. Seismic profiles reveal buried faults, such as Yurimori and Pangas Viejas, that lack surface expression. Post-earthquake deformation transitioned from the Cerro Prieto Fault to the Indiviso Fault, resembling slip-transfer processes observed in the San Andreas Fault system. Declining seismicity along the Cerro Prieto Fault contrasts with diffuse regional activity, underscoring the role of transform faults in accommodating interplate motion. Aftershocks were concentrated beneath sedimentary lowlands, while surface ruptures predominantly occurred in mountainous areas, influenced by lithostatic stress conditions. The primary rupture initiated along the northern Indiviso Fault zone, where differential stress reactivated pre-existing structures<b>.</b> Another aspect supporting this interpretation is that historical seismicity also shows a trend along the Indiviso Fault. The relocation of these identified two significant events that occurred in 1934 (Mw 6.5 and 6.3), as well as the 1935 event (Mw 5.7), distributed along this structure. This evidence indicates that the Indiviso Fault already existed and was tectonically active since that time. However, it is noteworthy that, prior to the EMC event, virtually no seismic activity was recorded in the region. These findings contribute to the understanding of fault reactivation, transform fault dynamics, and regional seismic hazard assessments.</p>