How much energy does an earthquake release?When an earthquake occurs, stress accumulated in solid rock is suddenly released along fault lines. The energy released when the rocks break along the fault is converted into seismic waves that radiate from the origin.
How much energy is involved largely depends on the magnitude of the quake: larger quakes release much, much more energy than smaller quakes. The Richter magnitude scale was devised by Charles F. Richter in 1935 to classify local earthquakes in southern California, but has evolved into the most common parameter to describe the size of the quake and hence, its energy and potential of destructive power.
It is logarithmic, meaning that an increase of 1 corresponds to a 10-fold increase in the amplitude of the seismic waves generated, which shake the ground. It can also be used to estimate the released energy of a quake, following the Gutenberg-Richter magnitude-energy relation:
log E = 1.5×R + 4.8
E = 101.5×R + 4.8
The relationship also involves that an increase of 1 in magnitude results in an approx. 30-fold increase in energy.
Seismic energy by magnitude compared:
|Magnitude||Energy in joules (J)||Wh||TNT equiv.||Notes|
|-2.0||63||0.0000175 KWh||near 0||1 kg dropped 6.30 m|
|-1.0||2000||0.00056 KWh||0.5 g of TNT||100 kg person jumps down 2 m|
|0.0||6.3 x 104||0.0175 KWh||15 g of TNT||60W light bulb turned on for 17 mins|
|1.0||2.0 x 106||0.56 KWh||0.5 kg of TNT||60W light bulb turned on for 9 hrs|
|2.0||6.3 x 107||17.5 KWh||15 kg of TNT||Only felt nearby|
60W light bulb turned on for 12 days
|3.0||2.0 x 109||556 KWh||0.5 tons of TNT||Energy from 50 liters of petrol|
|4.0||6.3 x 1010||17.5 MWh||15 tons of TNT||Annual energy consumption of 4 average UK households (US: 1.5)|
Often felt up to 10s of km distance
|5.0||2.0 x 1012||556 MWh||500 tons of TNT||Energy from 50,000 liters of petrol|
Annual energy consumption of 47 average US households
|6.0||6.3 x 1013||17.5 GWh||15 kilotons of TNT||1945 Hiroshima bomb|
Annual energy consumption of 1500 average US households
|7.0||2.0 x 1015||556 GWh||500 kilotons of TNT||Annual energy consumption of 47,000 average US households|
|8.0||6.3 x 1016||17.5 TWh||15 million tons of TNT||1–2 earthquakes this size each year|
Total annual energy use of Cuba
|9.0||2.0 x 1018||556 TWh||500 million tons of TNT||Total annual energy use of UK|
Some facts about earthquake energy:
- A single magnitude 8+ quake typically releases more energy than all other earthquakes combined during the same year (if no other quakes of similar magnitude occur).
- Magnitude 9+ quakes occur only every few years to decades on average, but account for significant part of the total seismic energy released during whole centuries.
- The largest recorded earthquake in history was the so-called "Great Chilean Earthquake" or "Valdivia Earthquake" which occurred on May 22, 1960 near Valdivia, in southern Chile. It had a magnitude of 9.5, which is also near the largest theoretically possible value. It accounts for about 30% of the total seismic energy released on earth during the last 100 years.
Sources / links:
- Earthquake magnitude calculations (British Geological Service)
- TNT equivalent (Wikipedia)
- Average Household Electricity Use (shrinkthatfootprint.com)
- List of countries by electricity consumption (Wikipedia)
- The 1960 Chile Earthquake Released Almost a Third of All Global Seismic Energy in the Last 100 Years (geovisualist)