Impacts of Earthquakes
An earthquake occurs when there is a sudden shift in rock masses beneath the Earth’s surface, resulting in the release of substantial amounts of energy that propagate as shock waves, causing vibrations. This movement is one of the planet’s internal forces that continuously reshape its surface. The Earth has experienced seismic activities for over four billion years, with thousands of earthquakes occurring daily. While most of these tremors are relatively minor, some are powerful enough to devastate cities and claim thousands of human lives. Earthquakes in the 20th century alone led to the loss of over a million lives. The potential danger associated with an earthquake depends on several factors, including the earthquake’s magnitude, its distance from populated areas, the intensity of seismic activity, and regional specifics like terrain, geological composition, building designs, and groundwater levels. Notably, significant earthquakes are often followed by a series of aftershocks. The following sections outline the major effects of earthquakes:
Ground Vibrations
Ground vibrations are the most common consequence of earthquakes. Their intensity can vary according to the strength of the seismic waves, ranging from mild tremors accompanying minor quakes to strong shakes during major seismic events. A powerful ground shake can last for several minutes, causing destruction and damage to structures, leading to the falling of objects, and making it difficult for humans and animals to maintain balance and mobility.
Cracks and Landslides
Sometimes, earthquakes cause ground fissures, although this is a relatively rare effect. These cracks form as a result of seismic shaking along a weak zone, such as a fault line, which leads to the fracturing of the Earth’s surface. Such ground fissures can pose serious risks to infrastructure, resulting in damage to pipelines, tunnels, waterways, railway lines, roads, and airport runways. Consequently, ground cracks in these areas can lead to severe destruction or significant disruptions.
Furthermore, earthquakes can trigger landslides due to ongoing vibrations and fissures, destabilizing slopes and causing rockfalls. Heavy rainfall and fractured rocks are additional factors that increase the likelihood and severity of landslides. These landslides can lead to the destruction of buildings, the washing away of homes, and the blockage of roads and railways, and, in some cases, can dam rivers.
Fires
Fires are another serious consequence of earthquakes. They can ignite due to gas leaks from broken gas pipes, electrical shorts in damaged power lines, or overturned burning wood or coal stoves. The situation becomes even more precarious if water supply lines are damaged, complicating firefighting efforts and allowing fires to rage for extended periods. This can result in the destruction of homes, leaving many residents homeless.
Tsunami Waves
Tsunami waves can occasionally emerge as a secondary effect of certain types of earthquakes. The term ‘tsunami’ originates from Japanese, meaning ‘harbor wave.’ A tsunami is a massive water wave generated by abrupt vertical shifts in the ocean floor due to earthquakes, landslides, or volcanic activity. Tsunamis originate from the area of disturbance on the ocean floor and can travel great distances, with their speed depending on the ocean’s depth; they can reach speeds of approximately 0.2 km/s (712 km/h). The height of tsunami waves often ranges from 10 to 20 meters, with some waves reaching as high as 90 meters.
While tsunami waves travel slower than seismic waves, the vibrations from an earthquake can serve as a warning for the impending tsunami. However, the time may be insufficient for residents near the earthquake’s epicenter to take precautions. It is important to note that tsunami waves are generally harmless in deep ocean waters, but they can become incredibly dangerous as they approach shorelines and shallow waters, where their energy is concentrated and their height increases. Tsunamis often cause more destruction and fatalities in coastal areas than the earthquakes that generate them.
Soil Liquefaction
Soil liquefaction occurs when water-saturated sandy soil experiences ground shaking due to an earthquake. This phenomenon causes the soil to lose its strength and rigidity, behaving like a viscous liquid. For soil liquefaction to occur, two conditions must be met: the soil must be loose sandy soil saturated with water up to a depth of about 9 meters below the Earth’s surface, and the ground shaking must be intense enough to trigger liquefaction. This process can lead to significant property damage globally, including the sinking and tilting of buildings, landslides, and cracking and settling of the ground surface.