For each increase of 1 unit in the Richter scale:
(1) the amplitude of the recorded earthquake wave increases by a factor of 10
(2) the energy increases 31.6 times
energy released in an earthquake in Joules =
= 10 ^ (4.8 + (1.5 * (Richter scale magnitude)))
or
LOG10(energy released in Joules) =
= 4.8 + (1.5 * (Richter scale magnitude)
A common misconception is that the Richter scale is logarithmic for energy release, rather than for amplitude of the wave amplitude.
The energy of the Hiroshima atomic bomb was about 2 * 10^13 joules, which is the amount of energy released in a magnitude 5.7 earthquake.
An earthquake with an magnitude greater than 7.0 on the Richter scale is considered a major earthquake.
Factors determining severity of damage from an earthquake at a given location include:
(1) amount of energy released, as indicated by the Richter scale
(2) distance of the location from the epicenter
(3) nature of underlying strata, with landfill and sand tending to be associated with more extensive damage
(4) shifts and gaps in the earth's crust, relative to buildings, highways and other structures
(5) preparedness of the community for earthquake damage, especially in construction codes
(6) secondary effects, including fire and tidal waves
