Secondary hazards are those that are caused by the primary hazards, and may be more catastrophic.
Tsunami
A tsunami is a series of ocean waves caused by a disturbance that moves the underwater land. Tsunami waves resemble normal waves but are tens of metres high. The time between waves can range from minutes to hours. The destructive power of tsunamis can be enormous and can wipe out cities. During the Sendai, Japan earthquake, more than 15,884 people died from the tsunami.
Flooding
Dam failure, triggered by an earthquake, will result in flooding of the downstream area, even in dry weather conditions. The failure of dams can lead to catastrophic floods from the rapid emptying of reservors to potentially drowning communities. Flooding can also cause major trouble in transport and could drown civilians. Tsunamis and Seiches can also cause floods and trap human beings inside causing death or severe injuries.
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Seiche
A Seiche is a standing wave in a partially enclosed body of water such as a swimming pool. Triggered from seismic waves, seiches have been observed from lakes, swimming pools, bay, harbours and seas. The key requirement for the formation of a seiche is that the body of water be partially bounded, allowing the formation of a standing wave.
Fire
Fire has always been recognized as a major hazard. Before the 20th century, earthquakes would often upset burning candles and lamps. Today, broken gas lines and electrical wires are most common sources of ignition. During the 1906 San Francisco earthquake, fire broke out across the city damaging the remaining structures. The fire killed more than 1,000 people. Fire also destroyed water, sewer pipes, telephones and transport facilities. Since water was lost, firefighters could no longer fight the fire and the loss of water could also have caused more deaths.
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