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Earthquake Damage to Transportation Systems
browse graphic Earthquakes represent one of the most destructive natural hazards known to man. A serious result of large-magnitude earthquakes is the disruption of transportation systems, which limits post-disaster emergency response. Damage to transportation systems is categorized in this set of images by cause including: ground failure, faulting, vibration damage, and tsunamis. This set of slides depicts earthquake damage to streets, highways, bridges, overpasses, and railroads. Earthquakes in Guatemala, Japan, Mexico, Armenia, and the United States are represented.A large magnitude earthquake near a populated area can affect residents over thousands of square kilometers and cause billions of dollars in property damage. Such an event can kill or injure thousands of residents disrupt the socioeconomic environment for months, sometimes years. A serious result of a large-magnitude earthquake is the disruption oftransportation systems, which limits post-disaster emergency response. Movement of emergency vehicles, such as police cars, fire trucks and ambulances, is often severely restricted. Damage to transportation systems is categorized below by cause including: ground failure, faulting, vibration damage, and tsunamis. Ground Failure - A principal cause of earthquake damage to transportation systems is seismically generated ground failures in the form of landslides, lateral spreads, differential settlements, and ground cracks. During strong ground shaking, areas of clay-free sands and silts (where groundwater is near the surface) can temporarily lose strength and behave as viscous fluids. Consequently, highways and railways may settle or tilt in the liquefied soil, or are ripped apart as the ground flows or spreads laterally. Ground failure can cause movement of large blocks of soil on top of a liquefied subsurface. The lateral spreads, which break up into many fissures and scarps, usually develop on gentle slopes. In the 1964 Alaska earthquake, lateral spread failures damaged streets and highways, and restricted the use of railway grades and bridges. Ground failure also can dislodge rock and debris on steep slopes, triggering rockfalls, avalanches, and earth slides. The dislodged material is deposited on highways and railways, blocking traffic for hours or days.Faulting - Earthquake surface faults sometimes cross highways and railroads. Where this occurs, the roadbed may shift in the horizontal or vertical plane, or Roadway buckling sometimes results from ground shortening where thrust faulting occurs, and distortion can result from drag rebound or from concealed, closely spaced fractures.