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Dublin: 16°C Tuesday 21 September 2021

How does an earthquake happen and why do they kill people?

The answer is they don’t.

Source: red Orbit/YouTube

TODAY, A SECOND violent earthquake hit Nepal, just 17 days after a devastating 7.8 magnitude quake left 4,000 people dead.

Early reports suggest that there are deaths, but it is not known how many.

Here in Ireland, we have little experience with major earthquakes, so it’s hard to fully grasp just how destructive they can be.

But in the last 25 years, just the five deadliest earthquakes have combined to cause the deaths of 680,000 people in Haiti, China, Pakistan, Iran and the Indian Ocean.

But, what is an earthquake?

Essentially, an earthquake is the sudden release of energy in the earth’s crust, which causes seismic waves.

These waves shake the earth or ocean floor and are measured on the Richter Scale, with anything under three being imperceptible and over seven being frequently deadly. Today’s Nepalese quake was a 7.4 and the first one was 7.8.

Nepal Earthquake A rescue worker from USAID inspects the site of a building that collapsed in an earthquake in Kathmandu. Source: Niranjan Shrestha

Sometimes, as was the case in both the Indian Ocean in 2004 and Japan in 2011, earthquakes cause tsunamis, which bring with them flooding.

The US Geological Survey defines an earthquake as:

An earthquake is what happens when two blocks of the earth suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocentre, and the location directly above it on the surface of the earth is called the epicentre.

They explain the earth’s surface as being like a “thick skin” of plates that is not all in one piece. These puzzle pieces move slowly around, sliding past and bumping into one another.

The plate boundaries are made up of many faults, and most of the earthquakes around the world occur on these faults.

When the plates meet, they create energy around the faults, which gets released outward like ripples on a pond. This causes the earth to shake.

Why do earthquakes kill people?

In reality, they don’t.

Standing in a wide open plain during an earthquake would be relatively safe. The problem is that that isn’t how people live.


Earthquakes kill people in developing nations because of two reasons: their proximity to fault lines and their poor building practices.

While there is no bulletproof idea when it comes to earthquake readiness, there are three guiding principles that are routinely ignored:

  • Build on bedrock
  • Tie buildings together to guard against toppling
  • Use steel and strong materials

In Haiti, one of the only buildings left standing was owned by Irish businessman Denis O’Brien’s Digicel.

TAIWAN QUAKE REFLECTIONS Taiwan was hit by an earthquake which it was woefully unprepared for in 1999. Source: AP/Press Association Images

Janise Rodgers from Geohazards International told Wired last month that the Nepalese capital of Kathmandu was not ready for the quake.

Seeing modern, vulnerable construction go up without engineering input, building codes, or thought to earthquake design made a lot of people very worried.

As Susan Hough and Lucile Jones of the US Geological Survey put it: earthquakes don’t kill people, buildings do.

Around three-quarters of earthquake deaths are caused by collapsing buildings.

Robin Cross of the charity Article 25 wrote in the Guardian just a fortnight ago:

Earthquakes are not just a “natural” crisis: they reflect a poverty crisis.

The worrying point, says Geohazards International, is that Nepal isn’t an isolated case. They say that Istanbul, Mexico City and parts of the US, as well as the Indian subcontinent are all vulnerable.

Read: Latest: At least 24 killed as new earthquake strikes devastated Nepal

Read: 101-year-old man pulled from rubble alive is surprised he survived second Nepal quake

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