Dam Failure

1. Dam Failure • Dams are generally an expensive structure that directly affect the economy of the area through power generation, flood control and water supply (reservoirs). As the population of an area grows, structural failure of a large dam due to an earthquake poses an increasingly great danger for residents exposed to sudden flooding. Failure of dam across the Kern River following the 1952 Kern County Earthquake

2. Van Norman Dam (Lower San Fernando Dam). For a length of about 1,800 feet, the embankment (including the parapet wall, dam crest, most of the upstream slope, and a portion of the downstream slope) slid into the reservoir. A loss of about 30 feet of dam height resulted when as much as 800,000 cubic yards of dam embankment was displaced into the reservoir. This material slid when liquefaction of the hydraulic fill on the upstream side of the embankment occurred. The dam was about half full at the time. Eighty-thousand people living downstream of the dam were immediately ordered to evacuate, and steps were taken to lower the water level in the reservoir as rapidly as possible.

3. The Los Angeles Dam was constructed to replace the Van Norman Reservoir. In the 1994 Northridge earthquake, some ground movement with minor cracking seems to have occurred at the site. There was significant differential settlement of the ground of about two inches in the northern section, and eight inches in the southwestern section of the site.

4. Damage to Transportation Systems • A serious result of a large-magnitude earthquake is the disruption of transportation systems, which limits post- disaster emergency response. Movement of emergency vehicles, such as police cars, fire trucks and ambulances, is often severely restricted. Collapsed Overpass Caused by 1971 San Fernando, CA Earthquake

5. Damage to Fourth Ave. Anchorage by the 1964 Alaska Earthquake Collapse of Spans on Bridge Due to 1976 Earthquake in Guatemala Compression of Railroad Track by 1964 Alaska Earthquake Collapse of Freeway in 1989 Loma Prieta, CA Earthquake

6. Freeway Compression Caused by 1971 San Fernando, CA Earthquake Collapse of Streets Caused by Subsidence in 1985 Mexico City Earthquake Damage to San Francisco-Oakland Bay Bridge 1989, Loma Prieta Earthquake

7. I-5 and SR-14 Freeway collapse North San Fernando Valley Northridge Earthquake 1994 Failure of I-10 in Culver City, Northridge Earthquake

8. The 1952 Kern County Earthquake (rupture seen above) caused serious damage to railway systems and dams (seen previously). Above right, compression of the ground surface has caused distortion of the railroad tracks. In the lower right photo, ground acceleration upwards was so great that it lifted the side of the tunnel up and dropped it on top of the rails to the side.

9. Damage to Water, Gas and Electrical Supplies • One generally takes the utilities water, gas and electrical for granted, and assumes that they will always be there. However, all of these major lifelines cross the San Andreas Fault at some point into the southern California area. In the eventuality of a large earthquake along the San Andreas, these would be cut.

10. The same is true for all major freeways systems and railways. These must cross the San Andreas at some point. In case of a major earthquake, there is a strong likelihood that these would be broken. Bending of rails due to compression of ground surface, Guatemalan earthquake, 1976 Bridge destroyed during 1976 Guatemalan earthquake

11. Bridge destroyed by liquefaction Costa Rican earthquake, 1976 Imperial Valley earthquake, 1979, water tower before (above) and after (below) quake Irrigation channels disrupted by 1976 Guatemalan earthquake