Earthquake Energy Calc
The Power of Exponential Growth
When you hear about an earthquake on the news, the difference between a Magnitude 5.0 and a Magnitude 6.0 sounds small. It's just one number, right?
Wrong. The Richter Scale is logarithmic. This means the scale multiplies rather than adds.
- Amplitude (Shaking): A Mag 6 shakes 10 times harder than a Mag 5.
- Energy (Power): A Mag 6 releases 32 times more energy than a Mag 5.
This means a Magnitude 8 earthquake is not "twice as bad" as a Magnitude 4. It releases nearly 1 million times more energy ($32^4$).
The Energy Formula
Scientists use the Gutenberg-Richter magnitude scale formula to estimate the energy yield in Joules.
Where E is Energy in Joules and M is Magnitude.
Richter vs. Moment Magnitude ($M_w$)
The term "Richter Scale" is actually outdated. Charles Richter developed it in 1935 specifically for California geology. It becomes inaccurate for massive quakes (above 8.0).
Today, seismologists use the Moment Magnitude Scale ($M_w$). It measures the physical movement of the fault line (area x distance slipped x rock rigidity). However, for news reports and general understanding, the numbers are scaled to match the old Richter numbers closely.
Real World Comparisons (TNT)
Energy in Joules is hard to visualize. Comparing it to tons of TNT gives a terrifying perspective.
| Magnitude | TNT Equivalent | Comparison |
|---|---|---|
| 3.0 | 1.8 Tons | Construction Site Blast |
| 4.0 | 56 Tons | Small Tactical Nuke |
| 6.0 | 56 Kilotons | Atomic Bomb (Hiroshima) |
| 8.0 | 56 Megatons | Tsar Bomba (Largest Nuke ever tested) |
| 9.0 | 1.8 Gigatons | Annual USA Energy Use |
The 2011 Tohoku Earthquake in Japan was a Magnitude 9.1. It released enough energy to power the entire United States for a year and actually shifted the Earth's axis, shortening the day by 1.8 microseconds.
Modified Mercalli Intensity Scale
While Magnitude measures energy at the source, Intensity measures what you actually feel on the ground. This depends on your distance from the epicenter and the type of soil you are standing on.
- I-III: Weak. Felt by very few.
- IV-V: Moderate. Dishes rattle, sleepers wake.
- VI-VII: Strong. Difficult to stand. Furniture moves.
- VIII+: Violent. Major structural damage.