Comment on "Late Quaternary Fold Deformation along the Northridge Hills Fault, Northridge, California: Deformation Coincident with Past Northridge Blind-Thrust Earthquakes and Other Nearby Structures?" by J. N. Baldwin, K. I. Kelson, and C. E. Randolph

Abstract

The 1994 Northridge earthquake in southern California spawned literally hundreds of investigations and their resulting publications. Many investigations are now deemed as paleoseismic , a term now widely used for good old-fashioned trenching and fault dating. Baldwin et al. (2000) continue this tradition by emplacing boreholes, a trench, and test pits across the face of a 2-m-high escarpment that marks the south side of the NW–SE–trending Northridge Hills in the northern San Fernando Valley. The Northridge Hills fault zone underlies the Northridge Hills, and interest in its ground-rupture potential was set forth over 50 yr ago by Hazzard (1944), and later by Slosson and Barnhart (1967), Barnhart and Slosson (1973), and Saul (1975), who basically concluded that fault movement occurred during late Quaternary time and that, therefore, the fault was likely to be active. In their article Baldwin et al. (p. 637) asked the rhetorical question: “Is the Northridge Fault active?” They answer in the affirmative, based mainly on interpretations of leveling data, on the construction of regional structural models, and on the inferred age of sediments exposed in trenches. …