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What causes an earthquake?
Answered by Planet Green
  • Planet Green

    Planet Green

  1. An earthquake occurs when a vibration moves through the Earth's crust, causing the ground to shake and shift. Technically, anything that causes the ground to vibrate is an earthquake. Many people believe that earthquakes happen only when the massive tectonic plates of the Earth move against each other. The shifting and colliding of these plates is certainly the main cause of earthquakes, but volcanoes, falling meteors and other occurrences can also cause the ground beneath your feet to move. Earthquakes can also be caused by humans -- for example, an earthquake might be triggered by a nuclear blast, the collapse of a coal mine or a large explosion of some kind. Even a rumbling semi-truck can set off a mini-earthquake as it passes your home.

    It's worth noting that not all earthquakes are so, well, Earth-shattering. They're capable of greater subtlety. For example, consider slow earthquakes. These are geologic events that aren't powerful enough to generate seismic waves but they still wind up affecting the distribution of stress beneath fault lines. They can occur over the course of days to months. In recent years, scientists have begun tracking slow earthquakes in an effort to more accurately forecast larger seismic occurrences. Researchers have noted such earthquakes along the famed San Andreas fault in California.

    A good example of a recent slow earthquake was one that researchers tracked in Hawaii in 2007. During two consecutive days in June of that year, Hawaii's Kilauea volcano experienced a dike intrusion (a crack in the Earth's crust that fills with magma) that caused a slow earthquake on the volcano's south side. Scientists were able to study satellite and GPS data to determine that the slow earthquake began about 15 to 20 hours after the dike intrusion, bringing with it smaller micro-earthquakes as well [source: Science Daily].

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