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.
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

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

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
 Tsunamis
are
caused by events
that drastically and
suddenly shift a
large volume of
water.
From Plummer McGeary Carlson
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 lowfrequency seismic energy.
These earthquakes present a problem for
tsunami warning systems
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.
Standard
Earthquake
M~7.0
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
From E. Okal
Slow-source Tsunami Earthquake
mb ~5.8, MS ~7.2, MW~7.7
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 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 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 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 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:

2D 
gl
v
tanh 
  L
 l  d  20 c
2

gD
Describing Ocean Waves

Shallow Water Velocity:
v  gD


The shallow water velocity does not depend on
wavelength. Shallow water waves do not show
dispersion.
 wave approaches shallow water the shape of
As the
the motion becomes more elliptical and the velocity
slows down. To conserve energy the wave rises
higher.
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)
v  gD

Typical tsunami wave velocity (water depth 5000m)
v~220 m/s = 792 km/hr (cruise velocity Jumbo 747
~800km/hr)

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.
2
gD2
H D1
vD 2


2
H D 2 v D1
gD1
From UNESCO/PTWC tsunami booklet
An Example

Tsunami Wave Example: Sumatra 2004
 How long does it take to get to Sri Lanka?
Distance ~1600 km
Water Depth ~4000 m
m
km
v  gD  9.8 * 4000 198  713
s
hr
T= 2000/713=2.2 hr

An Example

Tsunami Wave Example: Sumatra 2004
 How long to get to Thailand?
Distance ~500 km
Water Depth ~1500 m
m
km
v  gD  9.8 *1500 120  430
s
hr
T= 500/430=1.1 hr

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 Example

Tsunami Wave Example: Sumatra 2004
 How high is the wave?
2
gD2
H D1
vD 2


2
H D 2 v D1
gD1
2
2
gD2
H D1
0.6 2



2
2
HD 2 HD 2
gD1

1
9.8 *10
 H D 2  7.6m
9.8 * 4000

1
NOAA
QuickTime™ and a
GIF decompressor
are needed to see this picture.
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
 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
 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.
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
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

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.
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Bascom, 1964
86 feet = 26 m
QuickTime™ and a
GIF decompressor
are needed to see this picture.
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 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)
From Merritts et al., 1998
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 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
A emergency reaction example (thanks to Benz, USGS)
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Northern Sumatra
People are sensing severe
shaking
1 minutes after OT
NEIC
No information regarding
earthquake
P
S
PTWC
No information regarding
earthquake and/or tsunami
0
90
100
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Northern Sumatra
10 minutes after OT
Significant structural damage
in Banda Aceh
Tsunami inundation along the
Sumatran coast
EQ is widely felt throughout
the region
NEIC
P
S
Short period alarm on eight
stations in the region
PTWC
Short period alarm on western
Pacific stations
Short-period alarm stations
10 minutes after OT
10 minutes after OT
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Northern Sumatra
Tsunami inundation spreads
further along the Sumatran
coast
12 minutes after OT
NEIC
Short period alarm on sixteen
stations In the region
P
S
0
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
90
No tsunami advisor for the
Pacific Ocean
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Northern Sumatra
16 minutes after OT
Tsunami inundation spreads
further along the Sumatran
coast and reaches the
Nicobar Islands
NEIC
First automatic location released
at NEIC
P
S
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
01:14
Information Bulletin
WC&ATWC Tsunami
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.
16 minutes after OT
16 minutes after OT
30 minutes after OT
M5.5
34 minutes after OT
M6.1
M5.5
39 minutes after OT
M6.0
M6.1
M5.5
43 minutes after OT
M5.5
M6.0
M6.1
M5.5
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Northern Sumatra
Tsunami is passing thru the
Nicobar Islands
44 minutes after OT
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
0
Confers with NEIC on the
location and magnitude of the
earthquake
Notifies US Military on Diego
Garcia on the possibility of
an approaching tsunami
90
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Northern Sumatra
75 minutes after OT
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
0
PTWC
90
Telephone Call-Down List
USGS Earthquake Hazards Program Coordinator
USGS Office of Communications
USGS NEIS Coordinator
White House situation room
State Department Operations Center
FEMA Operations Center
International Commission on
Renal Failure, Alberta, Canada
EERI
USGS GHT Chief Scientist
USGS GHT Chief Scientist
USGS CR Executive for Geology
02:30 UTC
02:30
02:25
02:35
02:36
02:37
02:39
02:42
02:27
02:29
02:32
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
Recipients of “embassy” news release message
(Sent between 02:21 and about 02:30)
Msg. type
Fax/Email
US
Fax/Email
US
Fax/Email
US
Fax
UN
Agency
Embassy Consular Section,
Jakarta, Indonesia
Consulate General,
Surabaya, Indonesia
Consular Agent, Denpasar,
Indonesia
Office for the Coordination
of Humanitarian
Affairs, Geneva,
Switzerland
104 minutes after OT
104 minutes after OT
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Indian Ocean
122 minutes after OT
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
Propagation, Response and Warning Times
for the M9.0 Sumatra EQ
Indian Ocean
122 minutes after OT
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
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
 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)
 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.
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
 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
 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)
Landslide Tsunami
Sissano Lagoon - Papua New
Guinea
Earthquake Magnitude ~ 7.0
Landslide ~ 3-5 km3 [0.6 - 1.0 miles ]
Tsunami 10-15 meters [30 - 50 feet]
3
1929 Grand Banks
Earthquake Magnitude ~ 7.2
Landslide ~ 185 k m3 [~35 miles ]
Tsunami 4-12 meters [12 - 40 feet]
3
Mid-Atlantic Coast
Landslide ~ 150 k m3 [~30 miles ]
Tsunami ??????
3
New Jersey Coast
Landslide ~ 120 k m3 [~25 miles ]
Tsunami ??????
3
The 2004 Boxing Day Earthquake
1946 Hilo
Anchorage, Alaska – 1964
Anchorage, Alaska – 1964
Photographic sequence
from hotel balcony in
Thailand (1 of 2)
Photographic sequence (2
of 2)
Recognize fraudulent images Don’t be fooled