Paleogeodesy of the Sumatran Subduction Zone: - PowerPoint PPT Presentation

Title: Paleogeodesy of the Sumatran Subduction Zone:


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Paleogeodesy of the Sumatran Subduction Zone
Evidence of seismic and aseismic behavior
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Some fundamental questions about active faults

• What determines whether a fault fails seismically
  or aseismically?
• Does fault behavior vary with time?
• How uniform are slip events?
• In space?
• In time?

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Why go all the way to Sumatra to investigate
fault behavior?
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The Sumatran subduction zone is a large, isolated
fault, unlikely to be influenced by its neighbors
Outer arc ridge
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The Sumatran outer-arc ridge is largely above
water
Outer arc ridge
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and coral microatolls are abundant on its
fringing reefs
Outer arc ridge
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A small emergence event
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Submergence followed by emergence
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The sampling operation
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We have focused in two areas
This region of smaller earthquakes
And this region of very large earthquakes
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Bendera
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The microatoll graveyard in the intertidal zone
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uplift submergence
Pattern during seismic rupture
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submergence uplift
Basic pattern during interseismic period
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Bai
Bendera
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What about longer-term behavior?
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Low seismic rate, moderate events
High seismic rate, very large events
Why?
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Conclusions

• Behavior is localized geographically
• One region is predominantly aseismic
• An adjacent region is predominantly seismic
• These behavioral patterns persist over centuries
• Giant earthquakes occur in clusters with
  overlapping sources?

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• Work in progress
• Paleogeodetic studies south of the Equator
• modern rate variations along strike, rapid
  aseismic geodetic events, giant earthquakes
• 5 cycles of steady aseismic submergence and
  uplift during large earthquakes

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