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

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.

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

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