Destructiveness of an Earthquake
Name: ____________________________________ Period: ____ Date: _________
Essential Question: How does an earthquake become more destructive?
Seven Factors That Contribute to the Destructiveness of an Earthquake
A magnitude-6.3 earthquake shook Christchurch, New Zealand, collapsing buildings, triggering landslides
and flooding, and killing dozens of people. A more powerful magnitude-7.1 quake rattled another city
but didn't cause nearly as much damage, with no fatalities. Why do some earthquakes kill hundreds
or thousands of people while others do little damage? There are several factors that determine just how
destructive an earthquake can be:
1. Location: This one is kind of obvious—an earthquake that hits in a populated area is more likely to do
damage than one that hits an unpopulated area or the middle of the ocean.
2. Magnitude: Scientists assign a number to represent the amount of seismic energy released by an
earthquake. The Richter magnitude scale, as it is known, is logarithmic, so each step up represents an
increase in energy of a factor of 10. The more energy in an earthquake, the more destructive it can be.
3. Depth: Earthquakes can happen anywhere from at the surface to 700 kilometers below. In general,
deeper earthquakes are less damaging because their energy dissipates before it reaches the surface. The
recent New Zealand earthquake is thought to have occurred at a more shallow depth than the one last
year.
4. Distance from the epicenter: The epicenter is the point at the surface right above where the
earthquake originates ( focus or hypocenter) and is usually the place where the earthquake's intensity is
the greatest.
5. Local geologic conditions: The nature of the ground at the surface of an earthquake can have a
profound influence on the level of damage. Loose, sandy, soggy soil, like in Mexico City, can liquefy if
the shaking is strong and long enough, for example. That doesn't bode well for any structures on the
surface. Liquefaction takes place when loosely packed, water-logged sediments at or near the ground
surface lose their strength in response to strong ground shaking. Liquefaction turns soil and water into
mud. Liquefaction occurring beneath buildings and other structures can cause major damage during
earthquakes.
6. Secondary effects: Earthquakes can trigger landslides, fires, floods or tsunamis. It was not the 2004
Sumatran-Andaman earthquake that caused so much damage in 2004 but the Indian Ocean tsunami it
triggered. Nearly a quarter of a million people in 14 countries were killed when coastal communities
were inundated by the water.
7. Architecture and engineering designs: Even the strongest buildings may not survive a bad
earthquake, but architecture and engineering play a huge role in what and who survives a quake. The
January 2010 Haiti earthquake, for example, was made far worse by poor construction, weak cement
and unenforced building codes.
Read more: http://www.smithsonianmag.com/science-nature/seven-factors-that-contribute-to-the-destructiveness-of-an-earthquake44395116/#qUAxC3Chx7LxGWCd.99
R. Angat
Clarifying Questions:
1. What are the seven factors that contribute to the destructiveness of earthquakes?
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2. How can the location of an earthquake affect the destructiveness of an earthquake? Let
us say separate magnitude 7.1 earthquake happening in California and Alaska. Think!
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3. What does it mean by magnitude?
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4. How can magnitude affect the destructiveness of an earthquake?
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5. What does it mean by depth? Think!
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6. Which is more destructive a magnitude 6.3 shallow earthquake or a magnitude 6.3
deep earthquake? Think!
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7. Why did the New Zealand earthquake create a lot of damage? Think!
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8. What does it mean by epicenter?
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9. What is directly below the epicenter?
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10. The earthquake is strongest at the ________________________. ( epicenter or focus )
11. What happens during liquefaction?
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12. What causes liquefaction?
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13. How are structures like buildings, houses and bridges affected by liquefaction?
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14. What are the three secondary effects of earthquakes?
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15. How many people were killed in the Sumatran-Andaman earthquake in 2004?
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16. What mainly caused the death of nearly a quarter of a million people in the SumatranAndaman earthquake in 2004?
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17. How can the type the architecture and engineering designs cause more / less
earthquake destruction? Think!
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18. Why did so many died in the Haiti earthquake in January 2010?
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R. Angat