Earthquakes & Tsunamis

The ground beneath us often feels permanent and unshakable until, in a matter of seconds, it proves otherwise. Earthquakes are among the most sudden and destructive natural hazards, striking without warning and often hitting regions where large populations live. Each year, around a hundred earthquakes occur with enough strength to cause serious damage. When they affect densely populated areas, the consequences can be devastating, resulting in immense loss of life and long-term economic hardship.

An earthquake is the shaking of the Earth caused by the sudden release of energy from the Earth's crust (the‌ outer layer of the Earth that forms the tectonic plates)․ Plate movements are slow but continuous‚ and faults fractures in the Earth's crust that occur where the‌ plates meet build up stress over time and ultimately lead to earthquakes․ The edges of the plates are jagged and rough‚ and‌ they can catch on one another despite the motion of the plates․ Eventually‚ the rock becomes stressed and fractures; the energy is released as seismic waves resulting in an earthquake‚ which shakes the ground and everything resting on it‚ as it travels through the‌ Earth․.

Most earthquakes occur at the boundaries of tectonic plates‚ particularly‌ at subduction zones where one tectonic plate is being forced underneath another․ Most subduction zones are beneath oceans in‌ the so-called Pacific "Ring of Fire"‚ not coincidentally home to many of the world's largest earthquakes․ Earthquakes are‚ however‚ not‌ limited to plate boundaries․ Intra-plate earthquakes such as the 1811-1812 New Madrid earthquakes in the Mississippi Valley‌ have demonstrated that intra-plate earthquakes can happen in unexpected places․

Earthquakes can be‌ classified depending on how the plates are moving in relation to each other at the time of the earthquake‚ for example‚ in a strike-slip fault‚ they are sliding horizontally. The largest magnitude quakes occur at thrust faults‚ where one plate rides over another‚ or at normal faults‚ where one plate is pulled apart. Molten‌ rock oozes out to create new crust․ Regardless of the type, the sudden release of stored energy is what produces the shaking we feel.

Scientists measure earthquakes using instruments called seismographs, which record the vibrations of seismic waves. These recordings, known as seismograms, help determine an earthquake’s magnitude and location. While the Richter scale was once commonly used, it has largely been replaced by the moment magnitude scale, which provides a more accurate measure of the total energy released. Seismologists also use the arrival times of different wave’s faster P waves and slower S waves to locate an earthquake’s epicentre through a method called triangulation.

The effects of earthquakes extend far beyond the initial shaking. Secondary hazards often cause as much, if not more, damage. Landslides can be triggered on weakened slopes, floods may result from damaged dams, and fires can break out due to ruptured gas lines. In some cases, the ground itself behaves like a liquid in a process called soil liquefaction, causing buildings to tilt or collapse. Undersea earthquakes can generate tsunamis, as seen in the 2004 Indian Ocean disaster, which claimed hundreds of thousands of lives.

Historical examples highlight the varying impacts of earthquakes. The 2010 Haiti earthquake, with a magnitude of 7.0, struck a densely populated and economically vulnerable region, leading to over 200,000 deaths and widespread destruction. In contrast, the 1995 Kobe earthquake in Japan showed that even developed nations with strong infrastructure are not immune, though improved building standards helped reduce the overall impact. These events underline how preparedness and infrastructure quality play a crucial role in determining the outcome of such disasters.

In the aftermath of earthquakes, societies often face long-term challenges. Disruptions to water, electricity, and healthcare systems can lead to disease outbreaks and prolonged suffering. Rebuilding damaged infrastructure is costly and time-consuming, and stricter building regulations may increase future construction expenses. Yet, these challenges also drive progress, encouraging advancements in engineering, urban planning, and disaster management.

Despite their destructive nature, earthquakes also provide valuable insights into the Earth’s interior. By studying how seismic waves travel through different layers, scientists can better understand the composition and behaviour of the planet beneath our feet. While predicting the exact time and place of an earthquake remains beyond current capabilities, researchers can estimate the likelihood of future events in certain regions, allowing communities to prepare in advance.

Ultimately, earthquakes are a natural part of our dynamic planet, an essential process that releases built-up stress within the Earth’s crust. While they cannot be prevented, their impact can be reduced through awareness, preparation, and resilient infrastructure. By combining scientific knowledge with practical action, humanity can better coexist with this powerful force of nature and build a safer, more prepared future.

Did you know

1. Most earthquakes happen where tectonic plates meet, and a surprising number of them strike deep beneath the ocean floor, far from where we actually feel their effects.
2. The largest earthquake ever recorded, the 1960 Valdivia earthquake in Chile, reached a staggering magnitude of 9.5, reminding us just how powerful the Earth can be.
3. Earthquakes aren’t limited to one region. In the United States, for example, a major 1886 quake in Charleston, South Carolina (estimated magnitude 6.8–7.2) caused widespread destruction, showing that seismic risk exists even outside well-known zones.
4. Over time, scientists have learned that earthquakes happen every single day, but most are so small that we never even notice them.
5. Japan, sitting on multiple tectonic plate boundaries, experiences more earthquakes than almost any other country, making seismic activity a constant part of life there.
6. The Himalayas are still rising today, slowly but steadily, as the Indian and Eurasian plates continue to collide proof that Earth’s surface is always changing.
7. Some earthquakes originate incredibly deep, hundreds of kilometres below the surface, especially in subduction zones where one plate dives beneath another.
8. There’s a long-standing belief that some animals can sense earthquakes before they happen, though science hasn’t yet confirmed this idea.
9. In the immediate aftermath of an earthquake, it’s often ordinary people, not professionals, who become the first responders. With roads damaged and communication systems down, many survivors must rely on themselves for the first crucial days.
10. The health impacts don’t end when the shaking stops. In places like Haiti, the 2010 earthquake was followed by a deadly cholera outbreak that killed over 10,000 people and continued affecting communities for years afterward.
11. Earthquakes can leave deep economic scars. The 2010 Haiti earthquake, for instance, caused losses equivalent to up to 12% of the country’s GDP over several years pushing many people further into poverty.
12. Strong building codes can make all the difference. In 2010, Chile and Haiti were struck by powerful earthquakes just weeks apart, yet Chile suffered far fewer deaths due to stricter construction standards and better preparedness.
13. Recovery from a major earthquake is never quick. Even in developed countries like Japan, years after the 2011 disaster, thousands of people were still displaced, showing how long the road to normalcy can be.
14. And while recovery efforts continue, global attention and support often fade over time, making long-term rebuilding even more difficult, especially in vulnerable regions.
15. Today, modern early warning systems offer a small but critical advantage, giving people a few seconds of notice before strong shaking begins, just enough time to take cover and potentially save lives.