LATE QUATERNARY ACTIVITY OF THE LAGUNA-SALADA FAULT IN NORTHERN BAJA-CALIFORNIA, MEXICO

Faulted alluvial fans and bajadas along the central Laguna Salada faul t zone in northern Baja California record a recurrent history of obliq ue-slip Holocene earthquakes. Alluvial surfaces, which range from late Pleistocene to historic in age have been progressively displaced alon g the base of the crystalline rangefront, as well as along more basinw ard fault splays in alluvium. The recurrence interval determined from displaced alluvial deposits that are dated by soil profile development is in the range of 1-2 ka, with a corresponding right lateral slip ra te of approximately 2-3 mm/yr, similar to that of the southern Elsinor e fault in southern California. The most recent event along the fault zone is probably the widely felt earthquake of February 23, 1892. At l east 22 km of the fault zone ruptured during this event, along both an oblique-dextral section of the northwest-striking Laguna Salada fault and the linked, northeast-striking Canon Rojo normal fault. The lengt h of ground rupture and amount of displacement (4 m of dextral slip an d 3.5 m of normal slip) suggest that the earthquake had a magnitude (M w) of at least 7.1.