GPS Records Variable Deformation across a Subduction Zone

1min 17s Novice

How does deformation change the land above a subduction zone?

Recent data from the Pacific Northwest and other subduction zones show that there are 3 distinct areas of movement above a subduction zone: 1) constant movement above the locked leading edge, 2) see-saw pattern of back-&-forth movement above a zone that alternately locks then slips in a process called episodic tremor and slip , and 3) no movement far inland above the deeper part of the diving oceanic plate.

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Keypoints:

  • Subduction zones have variable stress
  • Three graphs represent compressional stress in different subduction regions
  • Near-trench overlying plate shows steady compression and deformation
  • The transition zone graph has a sawtooth pattern indicating periodic slip
  • Flat pattern inland indicates the subducting plate is not locked

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GPS can record the movement of the leading edge of the overlying continental plate in a subduction zone. The plates are locked and the overlying plate is forced back. When friction is overcome and strain is released, the GPS receiver will snap back toward its original position. 

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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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Related Lessons

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Lesson Intermediate