| 1 |
|
Earthquake Damage to Transportation Systems |
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.
|
