Tsunami Science: Sources, Generation, Propagation, Flooding

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Tsunami ScienceSources, Generation,
Propagation, Flooding

• Masahiro Yamamoto, Laura Kong, IOC
• Kuala Lumpur, Malaysia, 21-25 August 2006
• Male, Maldives, 27-31 August 2006
• Sri Lanka, 30 August 2006

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OUTLINE

• PLATE TECTONICS and
• EARTHQUAKES
• TSUNAMI SOURCES
• WAVE CHARACTERISTICS
• GENERATION and PROPAGATION
• TERMS
• DAMAGE and IMPACT

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Indonesia
Active volcanism characterizesRing of Fire where
plates subduct
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Types of Earthquake Faulting - Normal fault -
Thrust or reverse fault - Lateral slip or
strike-slip fault
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Tsunami
Compound Japanese Word tsu nami harbor
wave
Tsunami is a set of ocean gravity waves caused by
any large, abrupt disturbance of the ocean
surface.
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TSUNAMI GENERATIONWhere and How

• GENERALLY by EARTHQUAKES
• LESS COMMONLY by SUBAERIAL-to-
• SUBMARINE LANDSLIDES
• INFREQUENTLY by
• VOLCANIC ERUPTIONS
• VERY RARELY by METEORITE IMPACTS

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Seismicity (1964 - 2000)
Updated global data set Engdahl et al. (1998)
S. Widiyantoro, Indonesia Training, May 2006
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TSUNAMISGENERATED BYEARTHQUAKES
Large EQ (gt7.5)Shallow EQ at or near the
seafloor (lt 50 km)Subduction zones Sudden
displacement moves overlying column of water
generating wave
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METEORITEIMPACT

• None in
• recorded
• history
• Most burn
• as enter
• Earths atmosphere

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Seismic and Tsunami Waves
Seismic Waves 20,000 mph Tsunami Waves 500
mph
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Determination of Hypocenter
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Earthquake Magnitude and Tsunami
M1?Displacement3, Length3
Richter Scale Magnitude
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Tsunami Source Regions
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Catastrophic Landslidesduring the young
evolution of shield volcanoes (Hawaii slides)
Heights up to 400m, inland up to 7km
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TSUNAMIS - What and How

• VOLCANIC ERUPTIONS - 1883 Krakatau

Local tsunami
Violent eruption creates impulsive disturbance,
Displaces great volume of water,Generates
destructive tsunami in source area.Sources
Explosion, Flank Slope failure,
Explosion/collapse of magma chamber.
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TSUNAMIS - What and How

• SPEED DEPENDS ON WATER DEPTH
• Fast in deep ocean (gt1000 km/h)
• Slows near shore (30-50 km/h)
• HEIGHT DEPENDS ON WATER DEPTH
• Small in deep ocean
• (few cm to 1 m)
• Grows near shore
• (can be gt30 m)

April 1, 1946 Tsunami , Hilo, Hawaii Maximum
flooding 6 meters
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TYPES OF OCEAN WAVES
TYPE CAUSE TIME /
CYCLE SEA SWELL WIND 2 -
25 SEC TSUNAMIS RAPID OCEAN 5 - 60
MIN DISPLACEMENT
TIDES ASTRONOMICAL gt
12 HRS CYCLES
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TSUNAMI SPEED
Speed g x h g acceleration of gravity
10 meters / second2 h water depth If water
depth is 5500 meters, then Speed 10 x 5500
m2/s2 234 m/s 524 miles/hour!
about 1000 km/hour
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Tsunami Propagation Speed
220m/s (800km/h)
10m/s (36km/h)
30m/s (110km/h)
70m/s (250km/h)
1/2
Tsunami Speed (Water depth Gravity)
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Hilo, Hawaii, 1946
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TSUNAMI GENERATED BY EARTHQUAKE
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CALCULATED TRAVEL TIMES - PTWC
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ESTIMATED MAXIMUM GLOBAL WAVE HEIGHT
NOAA PMEL
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TSUNAMIS - What and How

• SERIES OF OCEAN WAVES
• 5 TO 60 MIN BETWEEN WAVE CRESTS

Arica, Chile
Peru Tsunami 23 JUN 2001 Ms 8.0
1 hr
Hilo, Hawaii
no data
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TSUNAMI DAMAGE what to expect ...
TSUNAMI - INUNDATION

• Runup and Inundation

1964, Alaska
1957, Laie
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26 DEC 2004, INDONESIA INUNDATION
German Remote Sensing Data Center, German
Aerospace Center
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TSUNAMI - RUNUP

• Runup and Inundation

1993, Japan
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RUNUP
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NICARAGUA TSUNAMI SEPTEMBER 2, 1992 168
CASUALTIES SURVEY TEAM MEMBER EXAMINES DEBRIS IN
THE TREE IS AN INDICATION THAT THE SEA REACHED
THIS HEIGHT HERE.
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RECESSION
First wave may be a receding wave.
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26 DEC 2004, SRI LANKA RECEDING WATERS
COMPLEX WAVE INTERACTION
Digital Globe
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TSUNAMI DAMAGE FLOODING
E. Okal, Northwestern Univ
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TSUNAMI DAMAGE COLLAPSE
E. Okal Northwestern Univ
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E. Okal, Northwestern Univ
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E. Okal, Northwestern Univ
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Thank you for your attention!
Matsushiro Seismological Observatory Nagano,
Japan
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Hawaii
Indonesia
Active Seismicity characterizesRing of Fire
where plates subduct
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Earthquakes delineate Crustal Plate boundaries
Hawaii
Indonesia
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Tectonic Earthquakes at Plate Boundaries -
Normal faulting at mid-ocean ridges -
Strike-slip faulting along transform faults
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Tectonic Earthquakes at Plate Boundaries -
Thrust earthquakes at subduction zones -
Volcanic island arcs built above subducting plate
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• Convection in the mantle drives plate motions
  Plates spread at ocean ridges, Descend at ocean
  trenches/subduction zones

Left Conceptual drawing of mantle convection
cells. Below a depth of 700 km, descending slab
begins to soften and flow, losing its form.
Right Similar to convection cells seen in
boiling water or soup, but does not take into
account huge differences in size, flow rates of
these cells.
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Seismicity (1964 - 1995)
S. Widiyantoro, Indonesia Training, May 2006
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LANDSLIDESLituya Bay, 1958 Rockfall slides
into bay PNG, 1998 EQ-triggered submarine
slope failure
Lituya Bay, Alaska, after huge,
landslide-generated tsunami, July 9, 1958. The
earthquake-induced rockslide (upper right-hand
corner) generated a 525 m splash-up immediately
across the bay, and razed trees along the bay and
across LaChausse Spit before leaving the bay and
dissipating in the open waters of the Gulf of
Alaska.
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Lituya Bay, 19583D Modeling show development of
local eddies, huge run-up
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G. Gisler, LANL, USA
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• Landslide Tsunamis
• Can be every bit as destructive locally as
  Sumatra Tsunami
• Generally small or no far-field expression
• Weakly directional in far field
• Typically triggered by Earthquakes

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Landscape Seascape Evolution Todays
morphology gt Tomorrows stratigraphy Hazard
assessment Onshore/offshore
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Tsunami slow and grow as they near the coast. In
deep water, V500 mph They come ashore 30-50
mph. Still -- Cant outrun one to high ground.
Tsunami steepen in shallow water, but generally
do not become steep enough to break.
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Ocean waves Speed, wavelength height

• Sea Swell
• Short per 2 - 25 sec
• Wind-generated
• Tsunamis
• Long per 5 - 60 min
• Earthquake-generated
• In the deep ocean,
• less than 1 m,
• so cannot be
• felt on ship
• seen by air.

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Unlike regular waves, tsunami reach all the way
to the sea bottom. You cant out-dive a tsunami.
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CALCULATED TT OBS ARRIVAL TIMES
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TSUNAMI DAMAGE
E. Okal Northwestern Univ