Scientists measure the strength of earthquakes using several scales. The most important of them is the Richter scale, which ranks earthquakes by their magnitude from 1 to 10. Previously, measurements of vibration amplitude recorded by seismographs were used. Richter used the logarithmic scale. If the scale graph is presented as a curve, it can be seen that it is exponential – it rises sharply with increasing amplitude of tremors. Therefore, an earthquake of 10.0 on the Richter scale is not tremors of double intensity equivalent to 5.0. It could be a catastrophe 100 times greater than magnitude 5.0 earthquakes occurring annually in various regions of our planet. It should be noted that the strongest earthquakes known to humanity have not exceeded a magnitude of 9.5. Earth vibrations of magnitude 10.0 or greater have never been observed.
The most powerful disaster ever recorded in history was the Valdivia earthquake of 22 May 1960 with a magnitude of 9.5. The tectonic tremors were followed by a devastating tsunami, the consequences of which were felt throughout the Pacific region, including of the Hawaiian Islands and Japan. Areas where an earthquake with a magnitude greater than 9.0 can occur are Indonesia, Chile, Japan and British Columbia (Cascadia zone).
Magnitude or energy class?
The characteristics of tremors at the epicenter, associated with the strength of the seismic waves released during an earthquake, is referred to as the energy class (intensity). This measure is evaluated on a scale of 1 to 12. They are used to assess weak and moderate earthquakes. Thus, tectonic tremors with a magnitude of 4.0 correspond to an earthquake with an intensity of 7. An event with a magnitude of 5.0 would be equivalent to an earthquake with an intensity of 10-12. The result would be:
- massive destruction of buildings;
- dangerous damage to dams and dikes;
- ruptures and distortions of underground pipelines;
- appearance of cracks in the ground from 0.2 to 1.0 meters wide;
- formation of large landslides on riverbanks;
- formation of collapses and mudflows in mountains.
History provides many destructive disasters caused by seismic shocks with intensity of 10.
Intensity 10 earthquakes in history
The most destructive earthquake with an intensity of 10 (magnitude 6.8), which occurred at the end of the 20th century, was the seismic tremors with the epicenter in Spitak, Armenia. The catastrophe completely destroyed the city and led to the death of 25,000 people. On December 7, 1988, after the strongest earthquake, there was not a single surviving building left in the city, the infrastructure, railways and roads were completely destroyed. The survivors were left practically in an open field at sub-zero temperatures, without food, water or warm clothes. Several thousand more residents of Spitak died over the following days due to difficulties in delivering the necessary aid.
Another example can be considered the tremors from the eruption of the Krakatau volcano in 1883. The earthquake and the resulting tsunami with waves up to 40 meters high claimed the lives of over 40,000 people. A large number of casualties were avoided only because the catastrophe occurred in less densely populated regions of the Indian Ocean.
The Great Chinese Earthquake in the Shaanxi Province in 1556, with the intensity of 10.5, claimed the lives of 850,000 people and became one of the most destructive in human history.
According to chroniclers the Egyptian earthquake of 1201, which had the intensity of at least 10.0, claimed the lives of over a million people.
Potential effects of a magnitude 10.0 earthquake
Tectonic tremors with a magnitude of 10.0 can only occur in one region of the Earth known as the “subduction zone”, located in the Pacific Ocean and including the Ring of Fire. About 90% of all tectonic disasters in the world are recorded in this region, including major earthquakes with a magnitude of more than 8.5. This is due to the size of the tectonic plates and their unique characteristics in this region.
If an earthquake with a magnitude of 10.0 occurred in a subduction zone, it would release as much energy as a million nuclear bombs similar to the one dropped on Hiroshima. The city located 200 km from the epicenter will face complete destruction of all buildings, infrastructure and normal way of life during the initial tremors of such a powerful earthquake. Trees and old constructions will ignite from underground energy leaks, which will cause of fires.
After 30-60 seconds from the onset of the earthquake, similar consequences will spread to settlements located far from the epicenter. Considering the nature of the earthquake, soil and crust structures, it is expected that these cities will suffer the same fate as those located at the epicenter. A magnitude 10.0 earthquake will affect all regions of the world, and there will no longer be a safety zone on the entire planet.