TSUNAMI GENERATION MECHANISMS
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Transcript of TSUNAMI GENERATION MECHANISMS
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TSUNAMI GENERATION MECHANISMS
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Earthquake Parameters
• Moment measures earthquake strength.
• Mechanism specifies the orientation of the earthquake fault and the direction of slip on it.
• Earthquake depth :deep earthquakes would produce less potent tsunamis than similar shallow earthquakes.
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Earthquake Zones
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Faults: Strike Slip
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Faults: Dip Slip
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Faults: Dip Slip
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Fault Structures - Normal Faults
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Fault Structures - Reverse Faults
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Faults: Strike Slip
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Pull Apart Mechanism
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How does the earthquake generate tsunami?
When the bottom of the ocean was deformed
by this megathrust quake, the upward force
acted like that fist, creating massive waves of
tsunamis, which spread out in all directions.
Imagine a fist rising up from under the water.
Water rolls down off the sides of the fist.
NASA
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EARTHQUAKE INITIATION
Synthetic record sections of vertical tsunami motions at distances of 200, 500, 1000 and 2000km from point dip slip (top) and strike slip (bottom) earthquakes of magnitude Mw=7.5 and depth 10 km. Time runs for five hours and the peak amplitude of each trace is given in cm at the right. The lower half of the focal sphere and azimuth of observation are shown toward the right (Stewe Ward, Encyclopedia of Physical Science and Technology)
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Volcanic Eruptions
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• Animation
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Submarine Landslide
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Scientific terms:
Run-up: Vertical height a wave reaches
above a reference sea level as it washes ashore.
Wave height: Vertical measurement of the wave before it reaches shore.
Inundation distance: Horizontal distance a tsunami reaches landward from shoreline.
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USGS-NEIC
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Appearance of a tsunami when reaches the shore
A rapidly rising or falling tide
A series of waves
A bore
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Run-up height:
Tsunamis of distant origin: > 50 ft (15 m)
Tsunami generated near the earthquake
epicenter: > 100 ft (30 m)
First wave may not be the largest in
the series of waves.
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Do tsunamis stop once on
land?
Energy reflection back
Edge waves
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Complicated behavior of
tsunami waves near the coast !
The first run-up of a tsunami is
often not the largest.
Do not return to a beach several
hours after a tsunami hits.