Nepal earthquake, magnitude 7.3, strikes near Everest | Hacker News Reader

Nepal earthquake, magnitude 7.3, strikes near Everest

bbc.com

105 pointsilluminek19 comments

A magnitude 7.8 earthquake is 2.511 times bigger than a magnitude 7.4 earthquake on a seismogram, but is 3.981 times stronger (energy release).

via http://earthquake.usgs.gov/learn/topics/calculator.php

I did not quite understand "3.981 times stronger (energy release)", but god bless everyone.

The Richter scale is exponential. According to chrisra a 7.8 earthquake release almost 4x the energy of a 7.4 quake.

I didn't run the numbers, but it seems plausible the difference would be that big.

According to Wikipedia[1] a 7.5 quake releases 11 petajoules of energy, while a 7.8 quake release 32 petajoules.

[1] http://en.wikipedia.org/wiki/Richter_magnitude_scale#Example...

This is something that's always bothered me. The Richter scale is not, for normal people like myself, a good earthquake magnitude indicator. I always have trouble grasping that 7.5 and 7.8 are so far apart in terms of severity since my mind is set to find a .3 difference negligible. I would like to have a metric measurement of earthquakes that would allow me to more quickly understand the scale and size of a quake.

Edit: The difference between a 8.6 one and a 8.7 one is huge. The difference is as big as the difference between 0.0 and 8.35, in megatons at least.

Using Charles Richter's formula

Magnitude of Earthquake M = log I / S

(where I is the intensity of the earthquake taken 100km from epicenter, S is the intensity of a standard earthquake)

First earthquake 7.8 = log I1 / S

Second earthquake 7.1 = log I2 / S

If we solve this for I1/I2, we get 10 ^ 1.10 ~ 12.5

> The intensity of first earthquake was 12.5 times as intense as the later earthquake.

The richter scale in general is not a good indicator of the destructiveness of an earthquake. You need to consider the location of the epicenter and the depth of the quake before coming to any sort of conclusion.

I experienced this first hand here in Christchurch, NZ. We had a 7.1M quake and then a 6.3M aftershock 6 months later. Despite being almost an entire magnitude smaller the 6.3M aftershock was 10x more destructive. This was primarily because the epicenter of the 6.3M quake was 40km closer to the city and some unusually high verticle accelerations caused by the strike slip motion of the fault and the local geography.

http://en.wikipedia.org/wiki/2010_Canterbury_earthquake

http://en.wikipedia.org/wiki/2011_Christchurch_earthquake

The Mercalli Intensity Scale was developed to give a better indicator of the actual effect to people on the ground.

http://en.wikipedia.org/wiki/Mercalli_intensity_scale

The Richter scale is logarithmic and therefore, a doubling of values is not equivalent to a doubling of force.

Which doesn't account for the fact that this one is shallower than the previous earthquake. Shallower earthquakes create considerably more damage.

Please help the OSM HOT [1] team to map the regions struck by the earthquake. Without proper/up-to-date maps, coordinating emergency efforts is hardly possible.

[1] http://wiki.openstreetmap.org/wiki/2015_Nepal_earthquake

Please get used to how OSM works before starting to map. There has been lots of bad data added by new people to OSM in Nepal recently. Cleaning up may be more work than adding new.

Writing this from Kolkata (India). We were asked to evacuate the office building, as it was shaking. Just got an all clear to get back in.

God bless everyone.

That could be quite bad, because vast majority of houses in the area of Namche Bazaar has been built without steel-and-concrete reinforcement - just stones and cement, due to lack of motorable roads in Sulukhumbu region to supply steel and other building materials.

Can't believe another earthquake has hit Nepal and it's even worse. Please pray for the people of Nepal and donate. A little can make all the difference.

Aftershocks felt, there were at least 2. I ll call them major ones. I was sitting on 4th floor. It felt very strong.

Yes, 5.6 and 6.3 after 7.4.

Source: https://twitter.com/USGSBigQuakes

What's your location? Distance from initial epicenter?

Lots of Nepal Earthquake datasets (including map of new quake) on the Humanitarian Data Exchange:

https://data.hdx.rwlabs.org/nepal-earthquake

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