Earthquakes really pose little direct danger to a person. People can’t be shaken to death by an earthquake. Some movies show scenes with the ground suddenly opening up and people falling into fiery pits, but this just doesn’t happen in real life.
The most obvious danger brought by earthquakes is shaking ground. Depending on its intensity, this motion itself can damage or destroy building materials, which get stretched and bent beyond their tolerances. The ground’s movement can take the form of waves running along the surface of the ground. As the wave runs under a building, the structure can lean, potentially tipping over. Then, when the shaking stops, the ground often settles to a different level compared to where it was previously, causing buildings, roads, and other structures to become unstable, topple, or break apart. Shaking ground can also trigger other types of ground movement, unleashing landslides, avalanches, or mudslides, especially in mountainous regions.
Another phenomenon caused by shaking ground is soil liquefaction. This happens when the shaking ground stirs up groundwater, mixing this water with soil near the surface. The result is a new, soft soil mixture that behaves like quicksand. When soil liquefaction happens below a building, the previously stable soil underneath the structure transforms into mush, causing the building to sink, tip, or break apart. Once the earthquake stops, the groundwater will gradually seep back down into the earth, allowing the soil near the surface to become firm once again. As the soil firms, the building will stop settling and come to rest in its altered position. Liquefaction is particularly common in places with sandy soil and groundwater at shallow depths in the soil.
Earthquakes can also cause fires by pulling down power lines, ripping apart gas pipes, or toppling wood burning stoves or fireplaces. Although the resulting fires can vary in severity, their effect is often worsened as the earthquake disrupts emergency crews’ ability to extinguish them.Tsunamis and seiches can also cause a great deal of damage. A tsunami is what most people call a tidal wave, but it has nothing to do with the tides on the ocean. It is a huge wave caused by an earthquake under the ocean. Tsunamis can be tens of feet high when they hit the shore and can do enormous damage to the coastline. Seiches are like small tsunamis. They occur on lakes that are shaken by the earthquake and are usually only a few feet high, but they can still flood or knock down houses, and tip over trees.
Most of the hazards to people come from man-made structures themselves and the shaking they receive from the earthquake. The real dangers to people are being crushed in a collapsing building, drowning in a flood caused by a broken dam or levee, getting buried under a landslide, or being burned in a fire.
by: Ammara Siddique