
Deadly earthquakes are seismic disasters that result in a large number of human casualties. The deadliest earthquakes of the 21st century include the following seismic events:
- January 12, 2010, Haiti, magnitude 7.0 – 316,000 dead and 300,000 injured;
- December 26, 2004, Sumatra, magnitude 9.1 – 227,899 dead, tens of thousands missing after the tsunami;
- May 15, 2008, Sichuan Province, China, magnitude 8.1 – 87,652 dead;
- October 8, 2005, Pakistan, magnitude 7.7 – resulted in the death of 76,213 people;
- February 6, 2023, Turkey/Syria, magnitude 7.8 – the death toll reached 51,880 people.
What makes earthquakes deadly and why do some of them sometimes cause more casualties and destruction than others? The magnitude of an earthquake is not always enough to explain the number of casualties it can cause. The depth, type of ground movement, duration of tremors, as well as the occurrence of landslides or tsunamis as a result of seismic activity can make the situation worse. It is also necessary to consider factors such as population density, construction quality, and weather conditions during an earthquake.
Factors that make an earthquake deadly
The main indicator of earthquake power is the amount of energy released in the fault during the movement of tectonic plates. Earthquake magnitude is determined by the extent of activity in the fault zone and the force that caused the plates to move.
The magnitude 7.8 earthquake that struck southern Turkey in February 2023 is classified as major. An earthquake with a magnitude greater than 8 is considered powerful and causes catastrophic damage that can completely destroy settlements at the epicenter.
In addition to the magnitude, the duration of the tremors also influences the fatality rate of an earthquake. Usually, vibrations during small earthquakes last only a few seconds. But intense tremors from moderate to strong earthquakes, such as the 2004 Sumatra earthquake, can last more than a minute.
Depth of hypocenter
The magnitude of an earthquake is not the only factor that determines the destructive power of an earthquake. The distance from its hypocenter to the Earth’s surface is also important. For example, the Morocco earthquake’s hypocenter was located about 18 km below the Earth’s surface. This is about twice as high as Mount Everest, but by geological standards it is considered a shallow earthquake. This means there is less rock above the hypocenter to absorb the energy and vibrations. Therefore, the magnitude 7.2 earthquake of 2023 in Morocco was felt very strongly.
Time of occurence
Another significant factor determining the number of victims is the time of the earthquake’s onset. The Moroccan earthquake occurred at 23:11 local time, when most people were already asleep, and did not have time to leave their destroyed houses. This increases the number of casualties, as most earthquake deaths are caused by building collapses.
Earthquake-resistant construction
Building structures in earthquake-prone areas with seismic energy absorption capabilities can withstand tremors and vibrations, protecting everyone inside. Many Turkish experts criticized construction standards after the collapse of buildings during the 2023 earthquake. If the buildings had been constructed according to proper standards, even such a powerful earthquake would not have been able to destroy them.
Population density
The powerful 8.2 magnitude earthquake in Alaska in July 2021, a relatively deep quake that occurred far from major settlements, resulted in almost no casualties. Meanwhile, the less powerful Haiti earthquake was the deadliest in Latin America this century, resulting in hundreds of thousands of dead, injured and 1.5 million homeless. The high death toll is explained by the high population density – 27,000 people per square km.
Type of rocks
The chances of surviving an earthquake largely depend on the strength of the soil. If the soil is filled with marshy sediments, buildings on its surface are not able to withstand strong tremors. So, during the devastating Turkish earthquake of 2023, the city of Erzin, located just 80 km from the epicenter, remained almost completely unscathed. None of its residents were killed, and the buildings were unharmed. Geologists say that Erzin was saved due to its location on a dense layer of bedrock and harder soil capable of absorbing shock waves.
Emergency response
The speed and scale of emergency response is also crucial. Those who are trapped under the rubble need immediate assistance to survive. The speed of medical and humanitarian assistance will play a crucial role in saving the lives of earthquake victims.