Dams and Earthquakes

Dams & Earthquakes

(May 6, 2009) People involved in the design, construction and operation of large dams are normally particularly sensitive to earthquakes.

This is because of four factors:

1.  Dams are often built in active earthquake areas

2.  Reservoirs can trigger earthquakes

3.  Some water supply structures are susceptible to earthquake motion.

Embankments and outlet towers respond to earthquake vibrations. Shaking an unstable slope that has been weakened after saturation by rises in ground water levels may produce a landslide into the reservoir.

4.  The consequence of a dam or water supply failure is high.

The effects of a dam failure on people and structures downstream are dramatic and obvious. A more likely example of earthquake damage would be loss of control of the water supply.

The first two points will be examined in more detail.
Why are Dams Often Built in Active Earthquake Areas?

* Dams are usually built in valleys
* Valleys exist because active erosion is taking place
* Active erosion implies there has been recent uplift
* Under compressional tectonic force, reverse or thrust faults produce uplift
* Reverse or thrust faults dip under the upthrown block
* Therefore, many dams have an active fault dipping under them

Environmental Systems and Services Seismology Research Centre, May 6, 2009

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