Disaster risk management: Earthquakes

Maria was painting in the park when suddenly, the ground started shaking. She experienced an earthquake! Most earthquakes are caused by changes happening under the surface of the Earth in the crust. The crust is made up of large rock segments called tectonic plates that are constantly moving. Over time, this movement causes pressure to build up.

When the pressure becomes too great, the plates suddenly shift along a crack in the crust, called a fault. The shifting rocks release a lot of energy in the form of seismic waves. The waves spread through the rock in all directions, causing an earthquake. In the crust, the centre of an earthquake is called the focus. On the surface, it’s called the epicentre.

The closer people are to an earthquake’s epicentre, the more likely they are to feel its effects. The most common and immediately noticeable effect of an earthquake is ground shaking. This can feel gentle or very violent, depending on the size. An earthquake may even be powerful enough to change the surface of the Earth, creating cliffs and opening cracks in the ground. This is called surface rupture.

Rocks and soil can also be loosened from slopes, causing them to slide downhill, triggering landslides. Sometimes, shaking during an earthquake can even cause soil to lose its strength and behave like a liquid. This phenomenon is known as liquefaction, and it can cause buildings to sink or tilt. Earthquakes that happen under the ocean can also generate massive waves - tsunamis. And after an earthquake, there may be smaller tremors called aftershocks.

Aftershocks can continue for months or even years after a major earthquake. The earthquake Maria experienced wasn’t very strong. But strong earthquakes can become disasters. One reason why earthquakes can cause so much destruction is because they are unpredictable. Scientists called seismologists study earthquakes using tools that respond to ground noises and shaking - seismometers.

Using seismometers, they can identify patterns that tell us about possible risks. But, they can only calculate how likely it is that an earthquake will occur - not the exact time or place. Earthquakes can occur anywhere, but are most common in the regions near tectonic plate boundaries. We can’t stop earthquakes before they happen, so we must prepare. One way to minimise earthquake damage is to build structures that can resist the most powerful effects.

This may mean building structures with flexible foundations, and using strong and durable materials like reinforced concrete and steel. During an earthquake, steel structures can sway and absorb the shaking. Another way to minimise damage and keep people safe during earthquakes is to use technology. Early warning systems are a type of technology that can detect the very first seismic waves of an earthquake. They can then send out alerts to cell phones, TV stations, and even automated systems in buildings.

They provide valuable seconds to minutes of advance notice for people to take cover or move to safer areas. Recovery after an earthquake involves multiple phases. First, rescue crews need to make sure everyone is safe. If buildings have collapsed, people may need to be rescued. Next, emergency medical care, shelter, and food must be given to those affected.

Then, in the months and years that follow, property and major infrastructure like roads, bridges, railways, and airports must be repaired and rebuilt. Planners, architects, engineers, and contractors must work together to build better structures that can resist future earthquakes. Even when communities are prepared, getting back to “normal” can take a very long time. That is why managing the risks of earthquake disasters is crucial for creating safer and more resilient communities in earthquake-prone areas.