- journal_title：Environmental & ; Engineering Geoscience
- Contributor：JEFFREY A JOHNSON ; ROY J SHLEMON
- Publisher：Association of Environmental & Engineering Geologists
- Date：2013-02-01
- Format：text/html
- Language：en
- Identifier：10.2113/gseegeosci.19.1.41
- journal_abbrev：Environmental & Engineering Geoscience
- issn：1078-7275
- volume：19
- issue：1
- firstpage：41
- section：Articles
1">Still controversial is the origin of permanent ground deformation and infrastructure damage, including pipeline failures, associated with the M 6.7, 1994 Northridge, CA, earthquake in southern California. Based on site-specific studies, some researchers explain the deformation as failure due to seismic shaking. In contrast, we propose a tectonic origin, consistent with displacement on the primary rupture and with the tectonic geomorphology of the San Fernando Valley. A tectonic origin for the permanent ground deformation is based mainly on regional analyses including: (1) street-by-street mapping of fractures and infrastructure distress above the causative fault; (2) interpretation of post-earthquake aerial photographs; (3) comparison of the type, distribution, and pattern of fractures with early-1900s soil, geologic, and topographic data and 1920s aerial photographs; (4) review of four post-Northridge earthquake site-specific studies; and (5) the number and distribution of small-diameter pipeline failures. We find that the pattern of co-seismic fractures and folds and zones of concentrated pipeline failures all generally coincide with the contraction and resultant dilation and distortion of hanging-wall sediments. We thus conclude that a tectonic origin of the secondary structures and apparent association with local geologic and geomorphic features indicate a high potential for future similar deformation resulting in infrastructure damage and likely failure of critical pipelines.