1. Tsunamis

2. BANDA ACEH, INDONESIA: June 23, A satellite image of the waterfront area of Aceh province's capital city before the tsunami.

3. BANDA ACEH, INDONESIA: December 28, An image taken after the tsunami shows destroyed housing and the shoreline nearly wiped out.

4. 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.

5. 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.

6. 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.

7. Tsunami Genesis
Tsunamis are caused by events that drastically and suddenly shift a large volume of water.
From Plummer McGeary Carlson

8. 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

9. Tsunami Earthquakes
One way to identify these events is to compare Ms to Mw
Ms ~ 20 seconds period
Mw ~ seconds period
Since the signals are enriched in long periods the magnitude is unusually larger than the Ms estimate.

10. Slow-source Tsunami Earthquake mb ~5.8, MS ~7.2, MW~7.7
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

11. 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)

12. 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.

13. 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.

14. 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)

15. 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:

16. 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.

17. 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)

18. 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.

19. From UNESCO/PTWC tsunami booklet

20. 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

21. 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

22. Courtesy: K. Satake, unpublished
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

23. An Example Tsunami Wave Example: Sumatra 2004 How high is the wave? 21 1
NOAA

25. 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.

26. 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%

27. 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.

29. 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.

30. 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

32. 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:

33. 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.

34. Tsunami Travel Times (Hawaii)
From Merritts et al., 1998

35. 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.

37. 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

38. Sumatra Tsunami 2004
A emergency reaction example (thanks to Benz, USGS)

39. Propagation, Response and Warning Times for the M9.0 Sumatra EQ
Northern Sumatra
People are sensing severe
shaking
NEIC
No information regarding
earthquake
PTWC
earthquake and/or tsunami
1 minutes after OT P S 90 90
100

40. 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

41. 10 minutes after OT

42. 10 minutes after OT

43. 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
PTWC
Mwp8.2 earthquake located
off the north coast of Sumatra
No tsunami advisor for the
Pacific Ocean
12 minutes after OT P S 90

44. 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

45. 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.

46. 16 minutes after OT

47. 16 minutes after OT

48. 30 minutes after OT
M5.5

49. 34 minutes after OT
M6.1
M5.5

50. 39 minutes after OT
M6.0
M6.1
M5.5

51. 43 minutes after OT
M5.5
M6.0
M6.1
M5.5

52. 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 90

53. 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 90

54. 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 :42
USGS GHT Chief Scientist 02:27
USGS GHT Chief Scientist 02:29
USGS CR Executive for Geology 02:32

55. Msg Agency Pager/Email USGS Earthquake Program, Reston and Golden
Pager FEMA, Washington DC area
Pager/ UN Radio Readiness Group, New York
Fax/ Japan Meteorological Agency, Tokyo
Schweizerischer Erdbebendienst, Zurich,Switzerland
Servicio Hidrográfico y Oceanográfico de la Armada, Chile
Réseau National de Surveillance Sismique, EOPGS, Strasbourg, France
Seismic Data Analysis Center, BGR, Hannover, Germany
Russian Academy of Sciences Siberian Branch, Novosibirsk, Russia
GeoForschungsZentrum Potsdam, Potsdam, Germany
US Strategic Air Command, Nebraska
National Geospatial Intelligence Agency, Virginia
European-Mediterranean Seismological Centre, Bruyères-le-Châtel, France
Instituto Geográfico Nacional, Madrid, Spain
World Agency of Planetary Monitoring and EQ Risk Reduction, Geneva

56. Recipients of “embassy” news release message
(Sent between 02:21 and about 02:30)
Msg. type Agency
Fax/ US Embassy Consular Section, Jakarta, Indonesia
Fax/ US Consulate General, Surabaya, Indonesia
Fax/ US Consular Agent, Denpasar, Indonesia
Fax UN Office for the Coordination of Humanitarian Affairs, Geneva, Switzerland

57. 104 minutes after OT

58. 104 minutes after OT

59. 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
Wire service reports of
building collapse in Banda
Aceh
Web content is being
developed and posted
122 minutes after OT

60. 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
Wire service reports of
building collapse in Banda
Aceh
Web content is being
developed and posted
122 minutes after OT

61. 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

62. 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.

64. 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.

66. Rivers & Lakes

67. 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.

68. 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.

69. 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)

76. The 2004 Boxing Day Earthquake

83. 1946 Hilo

84. Anchorage, Alaska – 1964

85. Anchorage, Alaska – 1964

86. Photographic sequence from hotel balcony in Thailand (1 of 2)

87. Photographic sequence (2 of 2)

88. Recognize fraudulent images - Don’t be fooled