Low-angle normal faults are central to extensional tectonics yet remain controversial because their orientation is unfavorable for slip under Andersonian stress conditions, and large earthquakes on active examples are rarely documented. To address this debate, we investigate the late Quaternary earthquake record of the Cañada David detachment in northern Baja California, Mexico. Using drone-based photogrammetry (∼160 km2), high-resolution orthomosaics, and digital surface models (11−15 cm), we mapped fault scarps and alluvial fan sequences along the Cañon Rojo−Chupamirtos fault system, a major strand of the Cañada David detachment. From 99 topographic profiles, we quantified vertical displacements on successive fan surfaces, revealing systematic variations in offset with fan age and fault orientation. Correlations with paleoseismic trench data show that the Cañada David detachment hosted 15−27 large (∼M7) earthquakes over the past ∼60,000 years, with ∼2000-year recurrence intervals, often co-rupturing with the Laguna Salada fault. Although our results confirm that low-angle normal faults are fully capable of generating major earthquakes, such events may be difficult to identify because they may involve co-rupture with adjacent faults of distinct orientations or nucleation on steeper down-dip segments as predicted by the rolling-hinge model.
Cambrón-Rosas et al. (Tue,) studied this question.