Datadelve

Figuring out the scale of the Nepal tremors: 7.8 is three times bigger than 7.3

A man stands in front of his house in the early morning hours in Bhaktapur near Kathmandu, Nepal, May 14, 2015. Photo: Reuters  

When it comes to earthquakes, the magnitude readings might not readily bring to mind the scale and intensity of the damage they could cause; for instance how big was the 7.8 magnitude earthquake that rocked Nepal on April 25 compared to the 7.3 one recorded on May 12?

The 0.5 difference in magnitude translates itself into dimensions of size and energy release that might not be obvious to those of us who are used to linear scales.

Nepal has been experiencing many minor tremors following the quake of April 25. Most of these have been in the magnitude range 4 and 5; they are generally experienced by a lot of people but cause little destruction

It is when earthquakes move to the 6 range that they generally start causing significant damage; the higher the magnitude the more destruction they cause. Buildings that are well-designed and structurally strong might withstand the quake better.



An increase in scale by 1 involves a tenfold increase; an earthquake of magnitude 6 is ten times bigger than one of manitude 5. So a magnitude 8 earthquake is 1000 times bigger than a magnitude 5 earthquake and so on.

But even much more is the energy released during a quake, which is 31.622 times more when the magnitude increases by 1. So a magnitude 8 earthquake will involve the release of energy that is 31,622.776 times stronger compared to a magnitude 5 earthquake.

So there it is: the magnitude 7.8 earthquake that Nepal experienced on April 25 was 3.162 times bigger than the magnitude 7.3 aftershock that struck the country on May 12. It was 5.623 times stronger in terms of energy release.

(Data source: US Geological Survey)

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Printable version | Apr 10, 2021 10:36:34 PM | https://www.thehindu.com/opinion/blogs/blog-datadelve/article7205654.ece

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