Japan’s Earthquake &Tsunami

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Japans Earthquake Tsunami
(REUTERS)
(REUTERS)

• What does it mean for us as engineers?

(REUTERS/Kyodo )
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Magnitude 9.0 NEAR THE EAST COAST OF HONSHU,
JAPANFriday, March 11, 2011 at 054623 UTC
The earthquake occurred 130 km (80 miles) east of
Sendai and 373 km (231 miles) northeast of Tokyo.
Images courtesy of the US Geological Survey
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Magnitude 9.0 NEAR THE EAST COAST OF HONSHU,
JAPANFriday, March 11, 2011 at 054623 UTC
This is one of the largest earthquakes that Japan
has ever experienced. .
In downtown Tokyo, large buildings shook
violently. Elsewhere severe flooding occurred due
to a tsunami generated by the earthquake.
USGS
Part of houses swallowed by tsunami burn in
Sendai, Miyagi Prefecture (state) after Japan was
struck by a strong earthquake off its
northeastern coast Friday, March 11, 2011. New
York Times
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The earthquake caused some damage but the
tsunami was devastating
Tsunami waves swept away houses and cars in
northern Japan and pushed ships aground. The
tsunami waves traveled far inland, the wave of
debris racing across the farmland, carrying boats
and houses with it.
The tsunami, seen crashing into homes in Natori,
Miyagi prefecture. AP
Houses were washed away by tsunami in Sendai,
Miyagi Prefecture in eastern Japan, after Japan
was struck by a magnitude 9.0 earthquake off the
northeastern coast. New York Times
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Fires after earthquakes are often caused by
broken gas pipelines
CNN reported The quake rattled buildings and
toppled cars off bridges and into waters
underneath. Waves of debris flowed like lava
across farmland, pushing boats, houses and
trailers toward highways. A number of fires
broke out including one at an oil refinery which
was burning out of control.
Giant fireballs rise from a burning oil refinery
in Ichihara, Chiba Prefecture (state) after Japan
was struck by a strong earthquake off its
northeastern coast Friday, March 11, 2011. Los
Angeles Times
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• Lets take a look at tsunami as it hits the east
  coast of Japan
• http//www.bbc.co.uk/news/world-asia-pacific-12725
  646

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What do you know about tsunamis?
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• The speed of a tsunami wave in the open ocean?
• 15 MPH (speed of a fast distance runner)
• 75 MPH (speed of a car)
• 200 MPH (speed of Japans bullet train)
• 475 MPH (speed of a jet plane)
• 762 MPH (speed of sound)

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What do you know about tsunamis?
2

• A tsunami is a single wave.
• True
• False

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Globally, this is the 5th largest earthquake
since 1900 (or 4th depends on M).
Chile 1960
Alaska 1964
Sumatra 2004
Russia 1952
Japan 2011
Ecuador 1906
Chile 2010
Alaska 1965
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What do you know about tsunamis?
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• A volcano or an underground landslide can produce
  a tsunami.
• True
• False

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Tsunami (harbor wave)
Seismic sea waves (NOT tidal waves)
Caused by processes that abruptly move large
volumes of ocean water
earthquake
submarine volcanic eruption
coastal/submarine landslide or rockfall
extraterrestrial impact
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How do EQ cause tsunami?
http//geology.com/articles/tsunami-geology.shtml
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Tsunami causes

• Unless there is an underwater landslide,
  strike-slip EQ WILL NOT cause tsunami
• Most tsunami generated by subduction zones

• Chile
• Alaska
• Japan
• Cascadia
• Philippines
• Caribbean
• New Zealand

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The earthquake occurred on a subduction zone
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
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What do you know about tsunamis?
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• The height of a tsunami wave in the open ocean?
• 1 to 2 inches
• 1 to 2 feet
• 10 to 20 feet
• 30 to 50 feet

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Tsunami wavelength

• Long wavelengths (over 100 km)
• Periods longer than 1 hour

316,800 ft 60 miles
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Tsunami wave speed

• Travel at high speeds 400 to 500 mph (200
  yards/sec)

• Alaska to CA 4 to 7 hrs
• Alaska to Hawaii 4 to 6 hrs
• Chile to Hawaii 14 to 15 hrs
• Chile to Japan 22 to 33 hrs

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Projected travel times for the arrival of the
tsunami waves across the Pacific
Nearby the earthquake there are only minutes to
evacuate. However, in many other regions there is
advance warning.
A tsunami map shows projected travel times for
the Pacific Ocean. This map indicates forecasted
times only, not that a wave traveling those
distances has actually been observed.. NOAA
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Tsunami wave speed

• v speed
• g acceleration of gravity (9.8 m/sec2)
• d depth of ocean (m)
• deeper water means higher speed
• For d 4,600 m, v 763 km/hr
  (speed of jet plane)

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What happens when tsunami gets near shore?

• Tsunami slows down (shallower water)
• Example d 100 m, v 113 km/hr
• Wave gets taller
• ? gets shorter, T gets shorter

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Tsunami nears shore

• As wave gets into shallow water bottom of wave
  drags along ocean floor
• Top of wave still moving fast can cause cresting
  of wave, and breaking onto shore

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Scientists Forecast Wave Propagation
This tsunami propagation forecast model shows the
forecast maximum tsunami wave height (in cm).
Ocean floor bathymetry affects the wave height
because a tsunami moves the seawater all the way
to the floor of the ocean. This led to a Pacific
wide tsunami warning being issued.
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Tsunami run-up

• Run-up measurement of height of water onshore
  observed above a reference sea level
• Generally dont get big gigantic wave
• Water comes as a fast moving rise in tide that
  rapidly moves inland
• NOT JUST ONE WAVEmultiple waves coming in about
  ½ hour or so apart
• See tsunami wave simulator http//www.seed.slb.com
  /en/scictr/watch/living_planet/tsunami_wave/index.
  htm

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Energy in tsunami

• Loss of energy in a wave is inversely
  proportional to ?
• Since ? very long, little energy lost
• Waves can travel great distances and still be
  very distructive

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Damage due to tsunami

• Waves often full of debris (trees, cars, pieces
  of wood etc.)
• As the wave recedes, the debris drags more stuff
  with it
• Can recede as much as a km out to sea, leaving
  shoreline empty with flopping fish, boats, etc.
  on the bottom

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Local Damage from Tsunami

• 17 million in Santa Cruz
• Docks
• Boats (17 sunk, 50 damaged)
• 50 million statewide

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• Lets take a look at what Japan looks like before
  and after
• http//www.abc.net.au/news/events/japan-quake-2011
  /beforeafter.htm

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Detecting a tsunami

• Pressure recorder on bottom of ocean
• Buoy to communicate readings via satellite
• Tsunami Warning Centers issue warning

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Magnitude 9.0 NEAR THE EAST COAST OF HONSHU,
JAPANFriday, March 11, 2011 at 054623 UTC
The DART II system consists of a seafloor bottom
pressure recording (BPR) system capable of
detecting tsunamis as small as 1 cm, and a moored
surface buoy for real-time communications. DART
II has two-way communications between the BPR and
the Tsunami Warning Center (TWC) using the
Iridium commercial satellite communications
system. The two-way communications allow the TWCs
to set stations in event mode in anticipation of
possible tsunamis or retrieve the high-resolution
(15-s intervals) data in one-hour blocks for
detailed analysis. DART II systems transmit
standard mode data, containing twenty-four
estimated sea-level height observations at
15-minute intervals, once very six hours.
NOAA
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Tsunami Warning Centers

• Hawaii and Alaska
• When EQ considered capable of generating tsunami,
  send warning with estimated arrival time

• Once tsunami hits somewhere, tsunami watch
  established to monitor tide gauges and ocean buoys

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Tsunami Monitoring Systems
Locations of NOAAs National Data Buoy Center
(NDBC) DART stations comprising the operational
network.
Tsunami monitoring systems have been
strategically deployed near regions with a
history of tsunami generation, to ensure
measurement of the waves as they propagate
towards coastal communities and to acquire data
critical to real-time forecasts.
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Tsunami Warning

• When warning is issued low lying areas are
  evacuated
• U.S. Coast guard issues warnings over marine
  frequencies
• Some places have sirens

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Tsunami
How could you evaluate the level of risk due to
tsunami?
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Possible tsunami run-up zones
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Seiche
standing wave

• Standing wave in an enclosed or partially
  enclosed body of water (similar to sloshing in a
  bath tub)

• Generated by wind or seismic activity
• Often swimming pools experience a seiche during EQ

http//earthquake.usgs.gov/learning/glossary.php?t
ermseiche
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Seiche potential in Lake Tahoe

• Scientists at UNR have determined the seiches
  have occurred on Lake Tahoe in the past
• Low probability on average once every 2000 to
  3000 years
• Good page on seiches w/great animation
  http//earthguide.ucsd.edu/earthguide/diagrams/wav
  es/swf/wave_seiche.html