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Tsunamis. BANDA ACEH, INDONESIA: June 23, 2004 A satellite image of the waterfront area of Aceh province's capital city before the tsunami. BANDA ACEH, INDONESIA: December 28, 2004 An image taken after the tsunami shows destroyed housing and the shoreline nearly wiped out.

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slide2
BANDA ACEH, INDONESIA: June 23, 2004 A satellite image of the waterfront area of Aceh province's capital city before the tsunami.
slide3
BANDA ACEH, INDONESIA: December 28, 2004 An image taken after the tsunami shows destroyed housing and the shoreline nearly wiped out.
what is a tsunami
What is a Tsunami?
  • When mass movement, such as an earthquake or landslide, suddenly displaces a large amount of water from its equilibrium state a disastrous wave called a tsunami can form.
  • Tsunami literally translates from Japanese to “harbor wave” but are often call tidal waves because small, distant-source tsunamis resemble tidal surges.
tsunami sources
Tsunami Sources
  • Earthquakes (e.g. Sumatra, 2004: >200,000 people killed; Papa New Guinea, 1998: ~3,000 people killed)
  • Volcanic eruptions (e.g. Krakatoa, 1883: tsunamis killed 30,000 people; Santorini, 2002).
  • Mass Movement (e.g. Alaska, 1958: waves up to 518 m high formed in Lituya Bay).
  • Extraterrestrial Impacts - large impacts have the potential to create enormous tsunamis.
tsunami earthquake sources
Tsunami Earthquake Sources
  • Earthquakes that suddenly uplift or down-drop the sea floor generate tsunamis.
  • Generally such surface deformation is largest for reverse and normal faulting earthquakes, and small for transform faulting events thus the potential for tsunamis is lower for strike slip faults (e.g. the Balleny earthquake 1998 did not generate a tsunami). In general tsunami are generated by reversal faults.
tsunami genesis
Tsunami Genesis
  • Tsunamis are caused by events that drastically and suddenly shift a large volume of water.

From Plummer McGeary Carlson

tsunami earthquakes
Tsunami Earthquakes
  • Some earthquakes have generated very large tsunamis for their “size”. These events are called tsunami earthquakes.
    • Analysis of seismograms from these events suggest that they are the result of low-frequency seismic energy.
    • These earthquakes present a problem for tsunami warning systems
tsunami earthquakes1
Tsunami Earthquakes
  • One way to identify these events is to compare Ms to Mw
    • Ms ~ 20 seconds period
    • Mw ~ 100-200 seconds period
  • Since the signals are enriched in long periods the magnitude is unusually larger than the Ms estimate.
slide10

An earthquake with a big vertical component is more “tsunamogenic” than a purely horizontal event.“Slow” events with a long duration are also sources of larger tsunamis

Standard Earthquake

M~7.0

From E. Okal

Slow-source Tsunami Earthquake

mb ~5.8, MS ~7.2, MW~7.7

describing ocean waves
Describing Ocean Waves
  • Ocean waves are deformations of the sea surface.
  • Wavelength: distance between crests (l)
  • Wave height: vertical distance between crest and trough
  • Period: time between 2 successive crests to pass (T)
describing ocean waves1
Describing Ocean Waves
  • The deformation propagates with the wave speed while on average water remains in the same position (the water does not pile up on the beach).
  • Water moves in the propagation direction at the crest while moving in the opposite direction at the through.
  • Water of a deep-water wave moves in a circular orbit on a circle which diameter is decreasing downward. The motion become negligible at a depth of ~ half wavelength.
describing ocean waves2
Describing Ocean Waves
  • Energy moves in the propagation direction.
  • Most ocean waves are produced by wind bringing the energy from the wind offshore toward the coast.
  • The rate at which a wave loses its energy is inversely related to its wavelength. Long-wavelength waves can travel further.
describing ocean waves3
Describing Ocean Waves
  • Deep water waves are surface waves.
  • Deep Water: the water depth where a wave passing overhead is not discernable at the sea bed.
  • Deep Water Waves: the wavelength is < 1/2 Water depth (D)
describing ocean waves4
Describing Ocean Waves
  • Wind Waves: T~ 10-20s l~10-600m
  • Deep Water Velocity: v=l/T (v~1-30m/s)
  • The speed of deep water waves depends on wavelength, deep water waves are dispersive.
  • Shallow Water Velocity:
describing ocean waves5
Describing Ocean Waves
  • Shallow Water Velocity:
  • The shallow water velocity does not depend on wavelength. Shallow water waves do not show dispersion.
  • As the wave approaches shallow water the shape of the motion becomes more elliptical and the velocity slows down. To conserve energy the wave rises higher.
describing ocean waves6
Describing Ocean Waves
  • Tsunami Wave: T~3600 s l~800 km
  • Since the ocean has an average depth of 5 km it is always a shallow water wave, the velocity is increasing with ocean depth. (friction with the bottom lower)
  • Typical tsunami wave velocity (water depth 5000m) v~220 m/s = 792 km/hr (cruise velocity Jumbo 747 ~800km/hr)
describing ocean waves7
Describing Ocean Waves
  • Tsunami Wave: T~3600 s l~800 km
  • Since the long-wavelength waves lose less energy a tsunami can travel transoceanic distances with only limited energy loss.
  • In the deep ocean the amplitude of a tsunami is a few cm to few dm on a very long wavelength: it is not felt aboard a ship or seen from air in open ocean (but can be measured by buoy or satellite altimeter).
  • When a tsunami approaches the shoreline the velocity decreases (D diminish) and in order to conserve energy (proportional to v and H) the amplitude increases.
an example
An Example
  • Tsunami Wave Example: Sumatra 2004
  • How long does it take to get to Sri Lanka?

Distance ~1600 km

Water Depth ~4000 m

T= 2000/713=2.2 hr

an example1
An Example
  • Tsunami Wave Example: Sumatra 2004
  • How long to get to Thailand?

Distance ~500 km

Water Depth ~1500 m

T= 500/430=1.1 hr

an example2
An Example
  • Tsunami Wave Example: Sumatra 2004
  • “Correct” numerical model using observed source and high definition bathymetry of the front propagation

Courtesy: K. Satake, unpublished

an example3
An Example
  • Tsunami Wave Example: Sumatra 2004
  • How high is the wave?

2

1

1

NOAA

describing tsunamis
Describing Tsunamis
  • Tsunami wave height is the height of the wave at the shore.
  • Tsunami run-up height is the maximum height that the wave reaches on land.
tsunami locations
Tsunami Locations
  • Large subduction zones produce the most tsunamis. The Pacific, rimmed with subduction zones, has the most tsunamis.
    • Pacific ~ 80%
    • Atlantic ~ 10%
    • Elsewhere ~ 10%
tsunami propagation
Tsunami Propagation
  • Tsunamis are most devastating near the earthquake. They are larger and strike the region soon after the earthquake.
  • They also travel across entire oceans and cause damage and death thousands of miles from the earthquake.
local tsunami damage
Local Tsunami Damage
  • Damage close to the tsunami is usually more devastating.
  • Even small events can generate locally high waves. (For example in a bay the waves can be focused and increase their amplitude, a landslide triggered by an earthquake in a fiord in Alaska in 1958 created waves with a run-up up to 518 m high).
  • The warning time can be dramatically short.
wave diffraction
Wave diffraction
  • Waves that pass from a media where they move fast to a media where they move more slowly, are refracted, and waves that move around obstacles, are diffracted. This can highly influence the local damages resulting from the waves.

Bascom, 1964

86 feet = 26 m

tsunami warning
Tsunami Warning
  • Because tsunamis travel relatively slowly, we have a chance to warn distant regions of potential tsunamis.
    • These efforts provide strong arguments for real-time earthquake monitoring.
  • Alerts are issued routinely by cooperating governments.
  • Check out:
      • http://wcatwc.gov/
tsunami warning1
Tsunami Warning
  • As soon as an earthquake of magnitude >6.5 is located in the sea the alarm start.
  • Using computer simulations and maps like the one in the following slide scientists forecast the time of arrival in different locations.
tsunami travel times hawaii
Tsunami Travel Times (Hawaii)

From Merritts et al., 1998

tsunami warning2
Tsunami Warning
  • As soon as an earthquake of magnitude >6.5 is located in the sea the alarm start.
  • Using computer simulations and maps like the one in the following slide scientists forecast the time of arrival in different locations.
  • The use of Buoy and tide gauges help to verify the effective presence of a tsunami, the alarm is given.
tsunami warning3
Tsunami Warning
  • As soon as an earthquake of magnitude >6.5 is located in the sea the alarm start.
  • Using computer simulations and maps like the one in the following slide scientists forecast the time of arrival in different locations.
  • The use of Buoy and tide gauges help to verify the effective presence of a tsunami, the alarm is given.
  • Once that the alarm is given is necessary that the local communities have emergency plans, that they receive the messages, and that the population knows what to do
sumatra tsunami 2004
Sumatra Tsunami 2004

A emergency reaction example (thanks to Benz, USGS)

slide39

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Northern Sumatra

People are sensing severe

shaking

NEIC

No information regarding

earthquake

PTWC

No information regarding

earthquake and/or tsunami

1 minutes after OT

P

S

0

90

90

100

slide40

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Northern Sumatra

Significant structural damage

in Banda Aceh

Tsunami inundation along the

Sumatran coast

EQ is widely felt throughout

the region

NEIC

Short period alarm on eight

stations in the region

PTWC

Short period alarm on western

Pacific stations

10 minutes after OT

P

S

Short-period alarm stations

slide43

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Northern Sumatra

Tsunami inundation spreads

further along the Sumatran

coast

NEIC

Short period alarm on sixteen

stations In the region

Mb6.2, Mwp8.2 earthquake

located off the north coast of

Sumatra

Pager notification to duty

seismologists and others at

NEIC

PTWC

Mwp8.2 earthquake located

off the north coast of Sumatra

No tsunami advisor for the

Pacific Ocean

12 minutes after OT

P

S

0

90

slide44

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Northern Sumatra

Tsunami inundation spreads

further along the Sumatran

coast and reaches the

Nicobar Islands

NEIC

First automatic location released

at NEIC

Pager notification to about 10

people in the USGS

PTWC

Confers with NEIC on the

location and magnitude of the

Earthquake

Release Tsunami Information Bulletin

16 minutes after OT

P

S

slide45

01:14 WC&ATWC Tsunami Information Bulletin

Location 3.4 N, 95.7 E

BASED ON LOCATION AND MAGNITUDE THE EARTHQUAKE WAS NOT SUFFICIENT TO GENERATE A TSUNAMI DAMAGING TO CALIFORNIA - OREGON - WASHINGTON - BRITISH COLUMBIA OR ALASKA. SOME AREAS MAY EXPERIENCE SMALL SEA LEVEL CHANGES. IN AREAS OF INTENSE SHAKING LOCALLY GENERATED TSUNAMIS CAN BE TRIGGERED BY SLUMPING. THE PACIFIC TSUNAMI WARNING CENTER WILL ISSUE TSUNAMI BULLETINS FOR HAWAII AND OTHER AREAS OF THE PACIFIC.

slide51

43 minutes after OT

M5.5

M6.0

M6.1

M5.5

slide52

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Northern Sumatra

Tsunami is passing thru the

Nicobar Islands

NEIC

Automatic Ms magnitude is

calculated (Ms8.5)

Pager notification to about 30

people in the USGS

Aftershocks suggest Ms8.5 is

too low

PTWC

Confers with NEIC on the

location and magnitude of the

earthquake

Notifies US Military on Diego

Garcia on the possibility of

an approaching tsunami

44 minutes after OT

0

90

slide53

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Northern Sumatra

Tsunami reaches the Andaman

Islands, approaches the Thai

coast

NEIC

Releases reviewed

earthquake location and

magnitude (Ms8.5)

Pager notifications are sent

to 25,000 people

Call down list is activated

Wire service reports

of collapsed buildings in

Banda Aceh

PTWC

75 minutes after OT

0

90

slide54

Telephone Call-Down List

USGS Earthquake Hazards Program Coordinator 02:30 UTC

USGS Office of Communications 02:30

USGS NEIS Coordinator 02:25

White House situation room 02:35

State Department Operations Center 02:36

FEMA Operations Center 02:37

International Commission on

Renal Failure, Alberta, Canada 02:39

EERI 02:42

USGS GHT Chief Scientist 02:27

USGS GHT Chief Scientist 02:29

USGS CR Executive for Geology 02:32

slide55

Msg Agency

Pager/Email USGS Earthquake Program, Reston and Golden

Pager FEMA, Washington DC area

Pager/Email UN Radio Readiness Group, New York

Fax/Email Japan Meteorological Agency, Tokyo

Email Schweizerischer Erdbebendienst, Zurich,Switzerland

Email Servicio Hidrográfico y Oceanográfico de la Armada, Chile

Email Réseau National de Surveillance Sismique, EOPGS, Strasbourg, France

Email Seismic Data Analysis Center, BGR, Hannover, Germany

Email Russian Academy of Sciences Siberian Branch, Novosibirsk, Russia

Email GeoForschungsZentrum Potsdam, Potsdam, Germany

Email US Strategic Air Command, Nebraska

Email National Geospatial Intelligence Agency, Virginia

Email European-Mediterranean Seismological Centre, Bruyères-le-Châtel, France

Email Instituto Geográfico Nacional, Madrid, Spain

Email World Agency of Planetary Monitoring and EQ Risk Reduction, Geneva

slide56

Recipients of “embassy” news release message

(Sent between 02:21 and about 02:30)

Msg. type Agency

Fax/Email US Embassy Consular Section, Jakarta, Indonesia

Fax/Email US Consulate General, Surabaya, Indonesia

Fax/Email US Consular Agent, Denpasar, Indonesia

Fax UN Office for the Coordination of Humanitarian Affairs, Geneva, Switzerland

slide59

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Indian Ocean

Little communication from

Banda Aceh

Destruction in Pkuket

Tsunami hits Sri Lanka

NEIC

Continuing dialogue between

USGS scientists in Golden,

Reston and Menlo Park

No confirmation via wire

services of tsunami in the

Indian Ocean

Wire service reports of

building collapse in Banda

Aceh

Web content is being

developed and posted

122 minutes after OT

slide60

Propagation, Response and Warning Times

for the M9.0 Sumatra EQ

Indian Ocean

Little communication from

Banda Aceh

Destruction in Pkuket

Tsunami hits Sri Lanka

NEIC

Continuing dialogue between

USGS scientists in Golden,

Reston and Menlo Park

No confirmation via wire

services of tsunami in the

Indian Ocean

Wire service reports of

building collapse in Banda

Aceh

Web content is being

developed and posted

122 minutes after OT

slide61

Can We Do Better? Yes

  • Improved sensor networks in hazards areas of the world (seismic, tide gauge, ocean buoys) and coordinated distribution and processing of data
  • Better information content that can better assist emergency responders to assess the scope of the disaster
  • Coordination and integration with national, regional and local emergency response agencies and civil authorities
  • Education and training at national, regional and local levels of government and the general population
tsunami hazard mitigation
Tsunami Hazard Mitigation
  • We can warn people of potential tsunamis from distant earthquakes. Warning of near source tsunamis is much more difficult.
  • Prevention of tsunami catastrophes requires carefully planned use of low-lying areas.
    • This is not always possible, or affordable.
protecting yourself tsunami
Protecting Yourself (Tsunami)
  • Move to higher ground.
  • Wait until authorities give the go ahead to return to low-lying regions.
  • Watch for surges of water in rivers and streams near the coast.
  • If you feel a strong earthquake, don’t wait for a formal warning.
shaking rivers lakes
Shaking & Rivers & Lakes
  • Tsunamis are an ocean phenomena, but any large body of water can be at risk if a larger part of its water is suddenly displaced.
  • Collapsing river banks or lake bluffs can be hazardous to anyone on the water and disrupt river traffic, which can impact local economies.
seiches
Seiches
  • The sloshing of closed bodies of water during an earthquake is call a seiche.
  • Large earthquakes have produced seiches observed over large areas.
  • Although seiches have produced waves with a height of a few feet, damage was minimal.
landslide in lakes
Landslide in lakes
  • A much more serious hazard is a landslide that it a lake in particular artificial basins. In this case the wave generated can overtop the dam and/or cause the dam failure. The results can be devastating (e.g. Longarone, Italy, 1963, 1917 people killed)