Japan Earthquake and Tsunami
What happened?
• Large earthquake
• Earthquake hazards:
– Tsunami
– Ground shaking
– Liquefaction
– Landslides
• People and structures in the way of the
hazards = catastrohe
Note:
• Japan is a developed country: per capita
income is $32,433
• Well prepared for earthquakes in terms of
monitoring, education, and preparedness
• 8,000 fatalities and 12,000 missing
Japan was prepared. The earthquake and tsunami caused so much
destruction that emergency services and education of population were
not enough to save many lives.
What is an earthquake?
Release of stored energy
• Elastic rebound theory explanation to how
earthquakes occur
• Plate movement concentrates energy in crust
• When the stored energy exceeds the strength of
the crust, the crust ruptures
• The rupture generally occurs along faults because
this is the weakest point
Energy Released in terms of seismic waves
How do you know there is an
earthquake?
How Faulting Generates Earthquakes
• Movement on the fault causes a release in
energy
• As the energy passes through an area, the
vibration is felt
• The energy is transferred through the earth
and man-made structures
• The bigger the amount of slip the more energy
released and therefore, the more vibrations
are produced
Describe what you have felt during an
earthquake.
•
•
•
•
Jolt
Loud boom
Shaking back and forth
Rolling
Stand up: half the class move to the
front of the classroom the other group
move to the back of the classroom.
You will represent the transfer of energy through the Earth.
Compressional Wave (P-Wave) Animation
IRIS
Deformation propagates. Particle motion consists of alternating
compression and dilation. Particle motion is parallel to the
direction of propagation (longitudinal). Material returns to its
original shape after wave passes.
Next wave: energy is transferred differently
• The first person should bend at the waist
• As soon as your neighbor has completed the
motion, you should begin
• Energy is transferred in a shear motion
Notice…
• This motion takes a longer period of time to
complete
• Motion is more complicated
• Shear motion is perpendicular to wave
movement
Let go of your neighbor and stand a few
inches apart.
• The first person should bend at the waist
• Move, only if you feel this person move
• This represents energy transferred by shear
movement
What happened?
• Shear waves cannot travel through liquids
because of how energy is transferred.
Shear Wave (S-Wave) Animation
Deformation propagates. Particle motion consists of alternating transverse
motion. Particle motion is perpendicular to the direction of propagation
(transverse). Transverse particle motion shown here is vertical but can be in
any direction. However, Earth’s layers tend to cause mostly vertical (SV; in the
vertical plane) or horizontal (SH) shear motions. Material returns to its original
shape after wave passes.
Seismic waves
• Body waves initiate at the focus
• Leave in wave fronts moving in all directions
• Body waves
– Primary wave: transfers energy by compression
and dilation
– Secondary wave: transfers energy by shear
motion
Surface waves
• When the body waves hit the Earth’s surface,
body waves transfer energy as surface waves
Love waves transfer
energy in a shear motion
Rayleigh waves transfer energy in
an orbital motion (similar to wind
blown waves)
Rayleigh Wave (R-Wave) Animation
Deformation propagates. Particle motion consists of elliptical motions
(generally retrograde elliptical) in the vertical plane and parallel to the
direction of propagation. Amplitude decreases with depth. Material returns
to its original shape after wave passes.
Love Wave (R-Wave) Animation
Deformation propagates. Particle motion consists of elliptical motions
(generally retrograde elliptical) in the vertical plane and parallel to the
direction of propagation. Amplitude decreases with depth. Material returns
to its original shape after wave passes.
Schematic diagram illustrating students performing wave simulations. Student
holds a poster board or cardboard circle in front of his or her body and walks
forward (like the seismic waves propagating in the Earth). While walking, the
student moves their circle forward and backward (“push and pull”, for the P
wave), or up and down (transverse motion for the shear wave), or in a retrograde
ellipse (for the Rayleigh wave), or side to side horizontally (for the Love wave), as
shown above.
Earthquake Waves
• The seismic waves are recorded in a predictable
pattern.
• What information can a seismologist interpret from
this recording?
Seismometers are placed in the
ground
• Signal is sent to a
computer
• Transfers image to a
digital record
Seismic waves arriving recorded in
Portland, Oregon
Japan earthquake
Why such a large earthquake?
• Tectonic setting
• Convergent plate boundary
• Subduction zone: produce the largest
earthquakes
Trench: depression associated with
subducting plate
Japan is an island arc
• Oceanic crust subducts
under oceanic crust
• Heating of hydrated
oceanic crust, upper
mantle and sediments
• Hot material rises and
ultimately produces
lava flows and
pyroclastic eruptions
• Volcanoes and islands
are created
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
Globally, this is the 4th largest earthquake since 1900.
Great (M > 8) Earthquakes Since 1900
9.6
Chile 1960
9.4
Alaska 1964
9.2
Magnitude
Sumatra 2004
Russia 1952
9
8.8
Japan 2011
Ecuador 1906
Chile 2010
Alaska 1965
8.6
8.4
8.2
8
7.8
1900
1920
1940
1960
Year
1980
2000
2020
Japan is part of the Ring of Fire
Ring of Fire: trenches and associated
subduction zones that surround the Pacific
Ocean
Physical Layers of the Earth
Lithosphere: crust and
upper mantle
Tectonic plates are made
up the lithosphere
Lithosphere and asthenosphere
Tectonic Plates
Tectonic plates may be composed of oceanic crust, continental crust or
both types of crust. Describe the extent of the North American plate and
the Pacific plate.
Worldwide Seismicity
Tectonic Setting: complex
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
This earthquake was the
result of thrust faulting along
or near the convergent plate
boundary where the Pacific
Plate subducts beneath Japan.
This map also shows the rate
and direction of motion of the
Pacific Plate with respect to
the Eurasian Plate near the
Japan Trench. The rate of
convergence at this plate
boundary is about 83 mm/yr
(8 cm/year). This is a fairly
high convergence rate and
this subduction zone is very
seismically active.
Japan Trench
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
What does the pink line represent?
This earthquake occurred 130 km (80
miles) east of Sendai, Honshu, Japan and
373 km (231 miles) northeast of Tokyo,
Japan.
Images courtesy of the US Geological Survey
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
The map on the right shows historic
earthquake activity near the epicenter
(star) from 1990 to present.
As shown on the cross section,
earthquakes are shallow (orange dots) at
the Japan Trench and increase to 300 km
depth (blue dots) towards the west as
the Pacific Plate dives deeper beneath
Japan.
Seismicity Cross Section across the subduction zone
showing the relationship between color and
earthquake depth.
Images courtesy of the US Geological Survey
GPS network in Japan
Crustal Displacement
Foreshocks and aftershocks
• Small earthquakes
preceding and after the
main event
• Yellow: March 9 and 10
• Orange and red: 24
hours after earthquake
Foreshocks and aftershocks
• Yellow: M 5-6
• Orange: > 7
Fault Rupture
• 30-40 meters (90-120
feet) of upward
movement
• 300 kilometers (180
miles) long and 150 km
(90 miles) wide rupture
• Foreshock of M 7.2 and
several M 6 aftershocks
Aftershock: April 7th
• M7
• 30 miles: hypocenter
April 11, 2011
•
•
•
•
M 7.1
58 M 6 or >
2 : 7.8 and 7.9 on 3/11
M7: April 7 and 11
Tsunami Warning
Why did the earthquake cause a
tsunami?
• Shallow focus
earthquake
• Large volume of oceanic
crust displaced
• The movement of the
crust also displaces a
large volume of water
Tsunami
• One wave moves toward the shoreline,
another travels into the open ocean
Tsunami at the
shoreline
Not a gigantic version
of breaking wave
Very rapidly rising
tide, rushing inland
Sometimes water
retreats first
Tsunami
• Shallow water waves because as they travel across the ocean
and drag on the bottom (up to 18,000 feet)
• On the ocean’s surface, the wave is barely detectable (3 feet
high)
Shallow water waves
Velocity
• Increase in velocity with
an increase in depth
Tsunami: velocity
• Related to depth of ocean water
• Pacific Ocean: average depth 18,000 feet
• Velocities in the open ocean: >500 mph
Model of Cascadia 1700 tsunami
Tsunami, Japan, 2011
• 90 feet high
• Up to 2.5 miles of
inundation
• 8-10 minute warning
Village of Minamisanriku, where up to
10,000 people—60 percent of its
population—are now missing,
according to the Telegraph.
44 miles south of Sendai
Town of Yagawahama
Sendai Airport
Japan, 2011 tsunami
• Billions of dollars spent
• 40% of Japan’s
coastline contains up to
39’ high walls
• Tsunami destroyed
• 6 feet- wood structures
• 12 feet- concrete
destroyed
• 70 feet-everything
Gates close seconds after
earthquake
Projection of tsunami moving across
the Pacific Ocean
Period: the time it takes one complete
wavelength pass a point
• A series of waves may arrive every 10-60
minutes
Tsunami
• As the waves reach shore,
speed is reduced
• Height is increased
Shoreline arrival of tsunami
• Tsunami reach greater
height when they enter
harbor or other narrow
space
– 8 m wave on open
coastline  30 m wave
in narrow harbor
Narrow bay, deeper closer to shore
Same depth, farther from shore, open shoreline
Santa Cruz and Emeryville
Crescent City, California
Tsunami and You
• If You Feel the Earthquake
– Mild shaking for more than 25 seconds: powerful, distant earthquake may have
generated tsunami
– Sea may withdraw significantly, or may rise, before first big wave
– Water may change character, make unusual sounds
Japan’s tsunami warning system
Seismic recording stations
Tsunami warning system
Applied information from school project
• Noticed bubbles and
water retreated from
the shoreline
• Notified parents and
other hotel residents
• All moved to higher
ground
• Phuket, Thailand
Tsunami and You
• Tsunami Warnings
– Coastal Maps
• Tsunami-hazard map of Hawaii Big Island, based on local topography
• Coastline mapping of Indonesia, India and Sri Lanka after 2004 tsunami indicated
where human activities increased damage and loss of life
– Removal of vegetation, reefs increased impact of waves
– Buoys and Pressure Sensors
• Before 2004, NOAO operated six-buoy warning system in northern Pacific Ocean
• Funding since provided for 32 buoys around world, transmitting information to
scientists
• New tide-gauge stations and seismometers along coastlines
Pacific Tsunami Warning Center: 1967
• Alaska: west coast of North America
• Hawaii: the remainder portion of the Ring of Fire
• NOAA: National Oceanographic and Atmospheric
Administration
• Pacific Marine Environmental Laboratory
Deep-0cean Assessment and Reporting
of Tsunami: DART
• Goal is to reduce the
loss of life and property
• Eliminate false alarms
• Stations are positioned
in regions that
traditionally produce
tsunamis
Deep-0cean Assessment and Reporting
Tsunami-harbor
wave
of Tsunami: DART
• Seafloor pressure
recording system
• An acoustic link is used
to transmit data from
the pressure recording
system
• The data is relayed via
satellite
Deep-0cean Assessment and Reporting
Tsunami-harbor
wave
of Tsunami: DART
Early detection and realtime reporting of
tsunamis
• National Oceanic and
Atmospheric
Administration
(NOAA) responsibility
for hazard mitigation
DART locations: Indian Ocean