Earthquakes can sometimes result in great physical damage and in large loss of life. This damage can affect residences and commercial complexes, but can also extend to other infrastructure like bridges, sewers, and water and gas systems. The physical and human damage from an earthquake can vary a great deal, and can depend on a number of factors such as:

1. the magnitude of the earthquake. Amplitude of the seismic waves increases logarithmically with magnitude resulting in increased ground movement.
2. duration of the earthquake. The longer an earthquake lasts the greater the probability that the continued shaking of buildings will result in structural damage. Sometimes slightly weaker earthquakes of longer duration can cause even more damage than stronger short-lived earthquakes.
3. distance from the earthquake hypocenter (focus). The amplitude of the seismic waves decreases the further away you are from an earthquake’s hypocenter (focus).
4. the underlying material on which structures rest. Structures built on rock or solid ground are much more resistant to damage than structures built on loose rock and unconsolidated sediments.
5. the design of structures and the type of construction materials used. Structures that can bend and flex during an earthquake are much more stable than rigid structures. Wood frame buildings and steel frame buildings, for example, are fairly sturdy in withstanding earthquakes.
6. the time of day. Loss of life in earthquakes is usually higher during working hours (i.e., 9:00–5:00) because many people are in large buildings (i.e., schools, factories, office towers, etc.) during that time.
7. population density. Dense urban areas can often suffer high numbers of fatalities simply because there are large numbers of people in small areas.

Learning Activity

Where have the most damaging earthquakes in terms of fatalities occurred since the year 1900?

• Click here to see the locations of the ten earthquakes that have caused the greatest number of fatalities since 1900.

1. Country with the highest fatalities.
   
   
   1. Which country possesses more high fatality earthquakes than any other?
      
      China
   2. How many of the top 10 earthquakes occurred in this country?
      
      3
2. Earthquakes and plate boundaries.
   
   
   1. How many of these earthquakes occurred right on, or very close to a plate boundary?
      
      Six earthquakes occurred right on, or almost directly on a plate boundary.
   2. List these earthquake locations and the plate boundaries that are interacting at each earthquake location.
      
      
   1. Chimbote, Peru - the Nazca plate and the South American plate
   2. Messina, Italy - the African plate and the Eurasian plate
   3. Northern Pakistan - the Indian plate and the Eurasian plate
   4. Sumatra - the Eurasian plate and the Australian plate
   5. Kanto, Japan - the Pacific plate and the Eurasian plate
   6. Haiti – the Caribbean plate and the North American plate
3. Are the remaining earthquake locations near plate boundaries?
   
Most of the remaining earthquakes were near plate boundaries, but not in close proximity. The earthquake in Tangshan, China was the farthest from a plate boundary.

• Click here to add in the 10 largest earthquakes in magnitude since 1900.

4. Is there any overlap between the 10 most fatal earthquakes, and the 10 largest earthquakes since 1900? Where does this overlap occur?
   
   There is only one overlap: the earthquake in Sumatra.
5. Can you think of any reasons why the greatest number of fatalities data does not correspond exactly to the largest magnitude earthquake data?
Possible reasons could include the largest earthquakes did not always occur close to large populated areas, poor design and materials may have contributed to large fatalities from weaker earthquakes, when the earthquakes occurred, etc.