INVESTIGATES: Earthquakes

1. Earthquakes kill approximately 8,000 people each year and have caused an estimated 13 million deaths in the past 4,000 years.

2. The moment magnitude scale (MMS) replaced the 1930s-era Richter scale in the 1970s as the method of measuring the size of earthquakes in terms of energy released.

3. In Japan mythology, a giant catfish called Namazu is responsible for earthquakes.

4. The Indian Ocean earthquake in 2004 generated enough energy to power all the homes and businesses in the United States for three days.

5. An average earthquake lasts around a minute.

6. Aftershocks occur because the displaced fault line and crust are adjusting to the effects of the main earthquake. Larger earthquakes can have aftershocks that last for years.

7. Shock waves produced by Rayleigh waves or waves that roll through the Earth’s surface—in contrast to side-to-side waves or Love waves—can travel far enough upward to cause a disturbance in the ionosphere. The ionosphere is the layer of Earth’s atmosphere about 50-300 miles (80-480 km) above Earth’s surface.

8. Parkfield, California, is known as “The Earthquake Capital of the World” and has a bridge that spans two tectonic plates.

9. Earthquakes are mostly caused by geological faults, but they can also be caused by landslides, nuclear testing, mine tests, and volcanic activity.

10. The “focus” or “hypocenter” is the earthquake’s initial point of rupture. Its “epicenter” is the point at ground level above the hypocenter.

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