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Tsunamis/ Predicting Earthquakes

Tsunamis/ Predicting Earthquakes. Tsunamis.

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Tsunamis/ Predicting Earthquakes

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  1. Tsunamis/ Predicting Earthquakes

  2. Tsunamis • Tsunamis are hazardous ocean waves characterized by enormouswavelengths and highamplitudes that are triggered by a sudden disturbance. The most common disturbance is a large earthquake beneath the seafloor, but tsunami may also be triggered by volcanic eruptions, landslides or meteor strikes.

  3. Tsunami 1. Earthquakes that generate tsunami: • Very large, generally 7.3+ • Beneath the seafloor • Displace the seafloor a large distance upwards. • The sudden vertical motion pushes up a bulge on the sea surface that radiates outward as a tsunami wave.

  4. Starts with a M = 9.2 earthquake on the Indian Ocean Floor

  5. 2. Tsunamis have different characteristics depending on their location • In the open ocean: • Long wavelengths • Low amplitudes • Travels fast, 600 mph+ • Does not affect ships

  6. 3. Tsunamis have different characteristics depending on their location b. In the shallow ocean: • slows • Amplitude builds up • Very damaging • Most damage occurs as wave is receeding.

  7. Predicting Earthquakes 1.Precursorsare unusual events which predict earthquakes. We may eventually be able to use precursors to predict earthquakes, but not yet.

  8. 2. Seismic Gap Theory • Focuses on patterns in seismicity • Predictions based on irregularities • Also based on large gaps of inactivities • If a change in pattern occurs, there is an increased chance of an earthquake.

  9. 3. Common Precursors • Drop in water well levels • Gradual uplift of land near fault zone • Decrease in the number of microquakes

  10. d. Animal Behavior • Animals move to higher ground • Some animals come out of hibernation early • Refusal to go into pens • The Chinese successfully predicted an earthquake in 1975 by observing animal behavior.

  11. 4. Earthquake Warning Systems • Detect P waves before S waves hit. • Gives advance warning for 10 – 20 seconds • Japan and Mexico have an earthquake warning system • How much time before S waves hit?

  12. 5. Warning System Actions • Sirens to duck and cover • Trains stop • Gas lines shut off • Nuclear Reactors shut down

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