Earthquakes pose a significant threat to countries around the world. They are caused by the movement of tectonic plates and their size is usually described in magnitudes. This sudden, violent shaking of the ground can destroy buildings, infrastructure and even cause serious injuries or deaths.

Magnitude is based on measurement of motion recorded by a seismograph and it is indicated in whole numbers and decimal fractions. Magnitude scale has no upper limit, and it can indicate negative numbers too. So far, the largest earthquake recorded is magnitude 9.5 but even larger ones may be possible. Anyhow, small earthquakes are much more common than large ones. Most earthquakes are so small that they are not even felt by people.

The three largest earthquakes recorded are:

1. Chile, Valdivia (1960), magnitude 9.5
2. Alaska, Prince William Sound in (1964), magnitude 9.2
3. Indonesia, Sumatra (2004), magnitude 9.1

The largest earthquakes do not necessarily cause the largest damages, not when it comes to casualties at least. Some earthquakes produce tsunamis that cause a lot more damage killing people and destroying residential areas. Thus, the deadliest earthquakes since 1950 have been:

1. Haiti, Hispaniola (2010), magnitude 7.0 - more than 300,000 killed
2. China, Tangshan (1976), magnitude 7.5 - 242,000 killed
3. Indian Ocean (2004), magnitude 9.1 - 225,000 killed

An earthquake can cause primary effects, which are caused by the natural phenomenon itself or secondary effects, that are result of the primary effects. For example, broken water pipes would be a primary effect and poor sanitation a secondary effect (result of the broken water pipes). Even though earthquakes cannot be predicted, academia, scientists, engineers, professionals and policymakers come together to share knowledge for the benefit of humankind. They try to prevent catastrophes from happening and minimizing the damages that earthquakes cause. Precaution can be earthquake-safer building and restoration of damaged, for example culturally important buildings but also preparing society to possible natural catastrophes using regulations, training and education programs.

(You can read more about preparedness on our other blogpost!)


References:

BBC, 2023. Plate margins and plate tectonics. Bitesize.
https://www.bbc.co.uk/bitesize/guides/z2vjxsg/revision/1

Earthquake Hazard Program, 2023. Earthquake Magnitude, Energy Release, and Shaking Intensity. USGS
https://www.usgs.gov/programs/earthquake-hazards/earthquake-magnitude-energy-release-and-shaking-intensity

Kruhl, Jörn H., 2018 (eds.), Living Under the Threat of Earthquakes, Springer Natural Hazards.
https://doi.org/10.1007/978-3-319-68044-6_1

Michigan Technological University, 2023. How Do We Measure Earthquake Magnitude?
https://www.mtu.edu/geo/community/seismology/learn/earthquake-measure/

Rafferty, John P., 2013. The 6 Deadliest Earthquakes since 1950. Encyclopedia Britannica.
https://www.britannica.com/list/6-deadliest-earthquakes

SMS Tsunami Warning, 2023. Largest Earthquakes ever recorded.
https://www.sms-tsunami-warning.com/pages/highest-magnitude-earthquake

Vacareanu & Ionescu, 2022. Progresses in European Earthquake Engineering and Seismology – Third European Conference on Earthquake Engineering and Seismology – Bucharest, 2022; Springer Proceedings in Earth and Environmental Sciences
https://doi.org/10.1007/978-3-031-15104-0

Haiti, Hispaniola 2010 (Jorge Silva/Reuters)

Haiti, Hispaniola 2010 (Jorge Silva/Reuters)

Tangshan City 1976 (Bettman/CORBIS)

Indian Ocean areas 2004 (STR/AFP/Getty Images)