Mexico: Earthquakes & Tectonics

7min 46s Novice Spanish

How does Mexico's "Earthquake Early Warning" system work?

In 1985, a Great, magnitude 8.1 subduction zone earthquake occurred beneath the coast of Michoacan Mexico. Despite the 350-km distance from the earthquake epicenter to Mexico City, most of the 9,500 fatalities occurred there. That earthquake prompted Mexico to develop an earthquake alert system for all of Southern Mexico. This animation describes the tectonic and geologic process that affect the region, including concepts like magnitude, basin amplification, and building resonance.

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Keypoints:

Mexico City was affected by:

  • Amplification of surface waves due to sediment filled basin.
  • The specific resonance of medium-height buildings.
  • Weak structures

 

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The subduction zone iswhere two tectonic (lithospheric) plates come together, one subducting (diving) beneath the other. The plates are locked together and periodically overcome the friction causing the leading edge of the overlying plate to surge back, lifting a wall of water producting a tsunami.

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Subduction-zone megathrust earthquakes, the most powerful earthquakes in the world, can produce tsunamis through a variety of structures that are missed by simple models including: fault boundary rupture, deformation of overlying plate, splay faults and landslides. From a hazards viewpoint, it is critical to remember that tsunamis are multiple waves that often arrive on shore for many hours after the initial wave.

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