The Northridge quake: 3 images to view and download as GIFs, or order free as 35 mm slides

G. Marshall and R. Stein,

A 3-slide set: maps of the Northridge, California, earthquake setting, effects and deformations, USGS Open File Report, 94-442, 1994. (revised December 1996)

This set of slides captures the consequences of the 1994 M=6.7 Northridge, California, earthquake in three easily understood images. This event caused $12 billion in insured losses; the total losses were many times higher. The seismicity and faults are shown in the 'Setting' slide. The earthquake struck on a 'blind thrust fault,' meaning that the fault is inclined and does not reach to the earth's surface (see Stein and Yeats 1989 for examples). The first 10 days of Northridge aftershocks and ground cracking are shown. The surface faults activated during the adjacent 1971 M=6.7 San Fernando earthquake are also shown. This event also struck on a thrust fault. Surface-cutting faults thought to be active during the past 10,000 years are pink. Active folds, which conceal blind thrust faults like the one that ruptured in the Northridge shock, are green The principal effects of the earthquake shaking are shown in the 'Effects' slide, including the distribution of 'red-tagged' buildings (damaged to the point where occupants were barred from entry); bridge damage, landslides, ground cracking and surface faulting, liquefaction sites (where sand and water shot to the surface), and the region in which the peak ground acceleration exceeded 0.4 g, the nominal design acceleration formerly used for freeway overpass construction The permannent ground movement is shown in the 'Deformation' slide. Contours of predicted uplift are in blue and horizontal motions are in gold. Sites where the deformation was measured by GPS receivers are red triangles.The San Fernando Valley was uplifted 70 cm, or 2.3'.
3-Slides:
Effects of the earthquake: [Preview 180kb] [High resolution 4.3mb] - Red tagged buildings - Landslides - Strong ground motion	Tectonic and seismic setting of the quakes: [Preview 175kb] [High resolution 4.1mb] - main shock and aftershocks - known faults - previous surface ruptures	Deformation induced by the quake: [Preview 164kb] [High resolution 4.2mb] - GPS monitoring stations - Modeled deformation

The 35 mm slide set can also be mailed to you upon request free of charge.

The High resolution images can be used for PowerPoint presentation. If you neede higher resolution images, for poster-size prints for instance, contact us.

The digitally shaded relief was produced from the USGS 1: 100,000 scale Digital Elevation Models (DEM). Roads are from the U.S. Tiger files. Active Faults are from Charles W. Jennings, 1994, Fault Activity Map of California, California Division of Mines and Geology. Active Folds are from R. S. Stein and R. S. Yeats, 1989, Hidden Earthquakes, Scientific American, 260 (6), pp. 48-57. Faults and folds believed to be active during the past million years are depicted

• 1971 Surface Rupture corresponds to faulting associated with the 9 February 1971 M=6.7
• San Fernando earthquake, from Charles W. Jennings (1975), Fault Map of California.
• Harp, E. L., and R. W. Jibson, Inventory of landslides triggered by the 1994 Northridge, California earthquake, U.S. Geol. Surv. Open-File Rep., 95-213, 1995.
• Holzer, T. L., M. J. Bennett, J. C. T. III, D. J. Ponti, and R. v. Sharp (1996). Causes of ground failure in alluvium during the Northridge, California, earthquake of January 17. 1994. In 6th U.S.-Japan Workshop on Earthquake Resistant Design of Lifeline Facilities and Countermea-sures Against Soil Liquefaction, Tokyo: Nat. Cen. Earthquake Engin. Res.
• Hecker, S., D. Ponti, C. Garvin, T. Powers, T. Fumal, J. Hamilton, R. Sharp, M. Rymer, C. Prentice, and F. Cinti (1995). Ground deformation in Granada Hills and Mission Hills resulting from the January 17, 1994, Northridge, California, earthquake, U.S. Geol. Surv. Open-File Rep. 95-62.

• K.M. Hodgkinson, R.S. Stein, K.W. Hudnut, J. Satalich, and J.H. Richards, Damage and restoration of geodetic infrastructure caused by the 1994 Northridge, California, earthquake, U.S. Geol. Surv. Open-File Report 96-517 [1996] (text, map, CD-ROM), accessible via the internet at the site, http://www-socal.wr.usgs.gov/fema/.
• Hudnut, K. W., Z. Shen, M. Murray, S. McClusky, R. King, T. Herring, B. Hager, Y. Feng, P. Fang, A. Donnellan, and Y. Bock ( 1996). Coseismic displacements of the 1994 Northridge, California, earthquake, Bull. Seis. Soc. Amer., 86, S19-S36.
• Wald, D. J., T. H. Heaton, and K. W. Hudnut (1996). The slip history of the 1994,Northridge, California, earthquake determined from strong-motion, teleseismic, GPS, and leveling data, Bull. Seismol. Soc. Amer. , 86, S49-S70 , 1996.

• Strong Shaking (peak horizontal acceleration > 0.4 g, or 40% of the acceleration of gravity) contoured from roughly 50 strong ground motion stations by Carl M. Wentworth, Roger D. Borcherdt, Robert K. Mark, and David M. Boore (U.S.G.S., Menlo Park), unpublished map, and in preparation. Strong motion recordings from Anthony F. Shakal (C.D.M.G., Sacramento), Mihailo D. Trifunac (U.S.C.), and Ronald L. Procella and others (U.S.G.S., Menlo Park and Pasadena).
• Severely Damaged Buildings are blocks or individual buildings judged unsafe for occupation by inspectors of the Federal Emergency Management Agency, the Governor's Office of Emergency Services, the City and County of Los Angeles, and Ventura County.
• Damaged (minor to major) and Collapsed bridges from Caltrans (California Department of Transportation), Division of Structures, Post Earthquake Investigation Report.
• Buckle, I.G. (1994). The Northridge, California, earthquake of January 17, 1994: Performance of Highway Bridges, Tech. Rep. NCEER-94-0008. Nat. Cen. Earthquake Engin. Res., Buffalo.

Grant Marshall, now at SnapTrack, a QUALCOMM company, 675 Campbell Technology Parkway, Campbell CA, 95008,