Department of the Interior - U.S. Geological Survey

Inventory of Landslides Triggered by the 1994 Northridge, California Earthquake
Edwin L. Harp and Randall W. Jibson
Open-File Report 95-213
USGS Denver, CO 80225

The 17 January 1994 Northridge, California, earthquake (M=6.7) triggered more than 11,000 landslides over an area of about 10,000 km. Most of the landslides were concentrated in a 1,000-km area that includes the Santa Susana Mountains and the mountains north of the Santa Clara River valley. We mapped landslides triggered by the earthquake in the field and from 1:60,000-scale aerial photography provided by the U.S. Air Force and taken the morning of the earthquake; these were subsequently digitized and plotted in a GIS-based format, as shown on the accompanying maps (which also are accessible via Internet). Most of the triggered landslides were shallow (1-5 m), highly disrupted falls and slides in weakly cemented Tertiary to Pleistocene clastic sediment. Average volumes of these types of landslides were less than 1,000 m, but many had volumes exceeding 100,000 m. Many of the larger disrupted slides traveled more than 50 m, and a few moved as far as 200 m from the bases of steep parent slopes. Deeper ( >5 m) rotational slumps and block slides numbered in the hundreds, a few of which exceeded 100,000 m in volume. The largest triggered landslide was a block slide having a volume of 8X10E06 m. Triggered landslides damaged or destroyed dozens of homes, blocked roads, and damaged oil-field infrastructure. Analysis of landslide distribution with respect to variations in (1) landslide susceptibility and (2) strong shaking recorded by hundreds of instruments will form the basis of a seismic landslide hazard analysis of the Los Angeles area.

http://gldage.cr.usgs.gov/html_ files/ofr95-213/ABSTRAC2.html

(accessed February 3, 1998)

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