Transcript 074LessonsTsunami - University of Hawaii

On Dec. 26, 2004, a magnitude-9.0 earthquake off Indonesia's
Sumatra island unleashed giant waves that fanned out across the
Indian Ocean at jetliner speeds, leaving at least 230,000 dead
and millions of homeless in its wake.
Solomon
World’s Largest Magnitude Earthquakes
Earthquake
Magnitude
Year
Approx. casualties
1. Chile
9.5
1960
>2000
2. Prince William
Sound, Alaska
9.2
1964
 125
3. Andreanof
Islands, Alaska
9.1
1957
Not reported
4. Kamchatka
Peninsula
9.0
1952
Not reported
5. Sumatra
9.0
2004
>283,100
(>173,000 in
Indonesia)
 A tsunami is series of traveling ocean waves of extremely long length generated
primarily by earthquakes occurring below or near the ocean floor.
 Tsunami waves propagate across the deep ocean with a speed exceeding 800 km/h (
500 mph) and a wave height of only a few tens of centimeters or less.
 As they reach the shallow waters of the coast, the waves slow down and their height
increases up to tens of meters (30 ft) or more.
Earthquake and Tsunami
Not all earthquakes generate tsunamis.
An earthquake must have certain characteristics in order to
generate a tsunami:
1. Epicenter is underneath or near the ocean.
2. Fault causes vertical movement of the sea floor (up to
several meters) over a large area (up to 100,000 km2).
3. Large magnitude ( > 7.5 ) AND shallow focus ( < 70 km).
Source: Earthquakes by Bruce A. Bolt
“The 26th December 2004 Sumatra-Andaman earthquake is
the fourth largest earthquake in the world since 1900 and is
the largest since the 1964 Prince William Sound, Alaska
earthquake.”
United States Geological Survey (USGS)
“The tsunami that struck Southeast Asia on December 26, 2004 has
been confirmed as the most devastating in modern history.”
Guinness Book of World Records
Kuril Island, 8.1 M Earthquake
Jan 13, 2007
The Jan 13, 2007, Saturday quake struck at about 1:24 p.m. local time,
almost 500 kilometres east of Etorofu, the largest in a chain of four
disputed islands known as the Northern Territories in Japan, and the
Kuril islands in Russia.
Tsunami
Indonesian seacoast, 1800s.
A tsunami is generated on
the Convergent Boundary at
a Subduction Zone by a large
seafloor earthquake, 7 M
Zone
Earthquakes of magnitude 7 are generally
classified as major earthquakes, capable of
widespread, heavy damage.
Tsunami Warning
Sumatra Earthquake 9.2 magnitude on 26
Tsunami
26 december
December,
2004, triggered
a transoceanic
Indian Ocean Tsunami
The 2004 Asian Earthquake-Magnitude 9.3
Location:
OFF THE WEST COAST OF NORTHERN SUMATRA
The devastating megathrust earthquake of December 26th, 2004
occurred on the interface of the India and Burma plates and was
caused by the release of stresses that develop as the India plate
subducts beneath the overriding Burma plate. The India plate
begins its descent into the mantle at the Sunda trench which lies
to the west of the earthquake's epicenter. The trench is the
surface expression of the plate interface between the Australia
and India plates, situated to the southwest of the trench, and the
Burma and Sunda plates, situated to the northeast
Distances:
250 km (155 miles) SSE of Banda Aceh, Sumatra, Indonesia
310 km (195 miles) W of Medan, Sumatra, Indonesia
1260 km (780 miles) SSW of BANGKOK, Thailand
1605 km (990 miles) NW of JAKARTA, Java, Indonesia
Figure 2. Maximum tsunami amplitudes in meter predicted in Boussinesq model
simulations for the Bay of Bengal (x-long E; y-lat. N). Maximum run-ups up to 24 m
were predicted on the upper NW coast of Banda Aceh, Indonesia.
Plate Tectonics: Trying to
understand how the Earth
evolved is one of the
fundamental problems we
have in science.
On Earth's crust,
continental landmasses,
upon which we live, may
be thought of as ships
drifting upon a sea
(oceanic crust), propelled
wherever the currents
take them. This slow
voyage of the continents
has reshaped the face of
the Earth throughout its
history driven by internal
heat of the core.
Indonesia
At least 100,000 people are believed
dead in Aceh and Northern Sumatra,
while some 500,000 people are
sheltering in scattered refugee camps
across the province, the UN
estimates.
Large swathes of Banda Aceh,
Meulaboh and Calang and their
outlying districts are completely
destroyed.
To speed up aid delivery, the
Australian Air Force has assisted in
improving air traffic control at
Banda Aceh airport. The UN is
moving supplies by truck along the
road from the regional capital
Medan.
Other agencies are shipping relief by
sea to outlying islands. The ports of
Belawan and Lhokseumawe are the
nearest harbours undamaged by the
tsunami.
http://news.bbc.co.uk/1/shared/spl/hi/wor
ld/04/asia_quake/quake_maps/html/1.stm
Thailand
Worst affected districts are Phang
Na, Ranong, Trang, Phuket and
Krabi where more than 5,000
people are believed to have died.
These provinces form the heart of
Thailand's tourist industry. Some
27 hotel complexes in Phuket
alone have been destroyed, the
Thailand government reports.
At least 2,400 fishing boats have
been destroyed and 54,000 farm
animals killed, according to
official Thai estimates. Some
6,000 houses, 50 schools and 19
government buildings are also
reported to be damaged or
destroyed.
http://news.bbc.co.uk/1/shared/spl/hi/
world/04/asia_quake/quake_maps/ht
ml/2.stm
Image acquired and processed by CRISP/National University of Singapore
Image acquired and processed by CRISP/National University of Singapore
Sri Lanka
More than 30,000 people have
been killed and 835,000 have
been made homeless mainly in
the southern and eastern coastal
regions.
Worst affected districts are
Jaffna, Kuchaveli, Mullativu,
Trincomalee, Batticaloa, Ampara,
Hambantota, Matara and Galle.
Some 49,000 people are living in
refugee camps in Galle alone.
The United Nations and other
agencies are working to
distribute food, shelter and
supplies in these districts.
Tensions between the
government and Tamil Tiger
rebels are hampering aid
distribution to some parts of the
north east of the country.
http://news.bbc.co.uk/1/shared/sp
l/hi/world/04/asia_quake/quake_
maps/html/3.stm
India Hundreds of coastal
communities in India's
southern states of Kerala,
Tamil Nadu and Andhra
Pradesh have been devastated.
At least 9,000 people are
believed to have died.
Fishermen have been hit hard
with many losing the boats on
which they depend for their
livelihoods. Around 140,000
people are sheltering in relief
centres.
The Indian government has
estimated reconstruction costs
at around $1.6bn and has said
it will seek international aid for
long term reconstruction.
http://news.bbc.co.uk/1/shared/
spl/hi/world/04/asia_quake/qua
ke_maps/html/4.stm
Andaman and Nicobar Islands
India's Andaman and Nicobar
Islands lie close to the epicentre
of the earthquake. It is unclear
how many people died on these
remote, partly-tribal islands but
5,600 are missing – the vast
majority of India's missing total.
The islands' capital Port Blair has
continued to flood because of the
change in the sea level and
scientists said the earthquake's
impact was so tremendous that the
Andamans could have tilted or
even shifted. Six of the 38
inhabited islands have been
evacuated.
http://news.bbc.co.uk/1/shared/spl
/hi/world/04/asia_quake/quake_m
aps/html/5.stm
Burma Plate
Indian Plate
A. Between Earthquakes ‘Locked’ to the subducting mobile Indian plate, the overriding
Burma plate gets squeezed. Its leading edge is dragged down, while an area behind
bulges upward. This movement goes on for decades or centuries, slowly building up
stress. The time is 250 years as the Indian Plate is mobile and its movement has thrust
B. During an Earthquake An earthquake along a subduction zone happens when the leading edge
of the overriding plate breaks free and springs seaward, raising the sea floor and the water above
it. This uplift starts a tsunami. Meanwhile, the bulge behind the leading edge collapses, thinning
the plate and lowering coastal areas.
During a serious Earthquake
An earthquake along a subduction zone happens when the leading edge of the overriding plate
breaks free and springs seaward, raising the sea floor and the water above it. This uplift starts a
tsunami. Meanwhile, the bulge behind the leading edge collapses, thinning the plate and lowering
coastal areas.
C. Minutes Later
Part of the tsunami races toward nearby land, growing taller as it comes in to shore. This local
tsunami has no or very short warning time for the residents to away from the shore to higher
ground. Depending on the sea floor topography, another part heads across the ocean toward
distant shores.
Diagram showing how part of the energy from a seafloor earthquake is converted into sound that
travels through the ocean (as a T-wave). Oceanic earthquakes are detected more easily by
hydrophones than by seismometers on land
1. Recorder on sea bed
measures water pressure
every 15 mins - an unusual
result triggers a reading
every 15 secs.
2. Buoy measures surface
conditions and sends this
plus data from sea bed to
satellite
3. Satellite receives data and
relays it to ground stations
1. Float in a "stilling well"
tube measures sea level
2. Data is processed and sent
to satellite
3. Satellite transmits data to
alert centres
To detect and pinpoint earthquakes, the Warning Center relies on data
from a network of seismic stations. But not all earthquakes spawn
tsunamis, so they use coastal tide gauges and deep ocean pressure
sensors to figure out if one has formed. Located on the ocean floor, these
sensors monitor the depth of the water above them. A change could mean
a deadly tsunami is passing overhead. Data is relayed to a buoy on the
surface, up to a satellite, and down to the Warning Center. There are six
of these sensors in the Pacific Ocean.
Sunda Strait: Nov 2005, a German
buoy is anchored for monitoring
tsunams
Indian Ocean
Sea Level Stationa: Map showing location of GLOSS sea level stations and when they are to be upgraded.
The whole world watched in horror
as the tsunami disaster in the Indian
Ocean coastal areas unfolded. Large
amounts of money have been
donated and pledged, and enormous
logistical operations have been set
up. We are, however, only just
scratching the surface of this task.
U.S. Navy photo by Photographer’s
Mate 3rd Class Jacob J. Kirk
On land, seismometers are used to measure the shaking of the
ground from nearby earthquakes, but small earthquakes in the
oceans are usually too far away to be detected. In the ocean,
hydrophones are used instead to detect the faint rumbling sounds
from oceanic earthquakes. Hydrophones are better for detecting
oceanic earthquakes because sound waves (T-waves) travel much
more efficiently in water than P- or S- waves do in the solid earth.
In addition, the difference in travel time between P- and S- waves
can give the distance to an earthquake epicenter on land. In the
ocean, however, only the acoustic T-wave is recorded so the travel
time and earthquake epicenter must be calculated in a more
complicated fashion from many observations. Hydrophone arrays
can also give the direction to the epicenter, but cannot give any depth
information
Tsunami Warning Path
Earthquake
observation
Check SL data if
tsunami generated
If yes
Calculate epicenter
and magnitude
If>6.5
6.5<M<7.5: Info
7.5<M<7.8: Watch
>7.8: Warning
Issue Bulletin
Regional
Confirm Warning
TWC
National emergency
response (Evacuate or Stay alert)
Danger? decide based on
M, epicentre
If yes
National
TWC
IOC GLOSS
3 integral components
Objective of the System
• Develop national and regional capacity to:
– Assess national tsunami risk (Hazard
assessment)
– Promote preparedness and risk
reduction against tsunami hazard
(Mitigation and Public Awareness)
– Establish a national and regional
warning system against local and
regional tsunamis (Warning guidance)
WARNING CENTER OPERATORS
Pacific, Indian Ocean, Caribbean, Mediterranean
Tsunami
Warning Centers
GLOBAL
EMERGENCY
MANAGERS
Civil Defense
Local Authorities
REGIONAL
NATIONAL
TSUNAMI
SCIENTISTS
University and
Govt Researchers
Comprehensive Tsunami Risk Reduction
Stakeholders build Tsunami Resilient Community
SEISMOGRAPHIC NETWORK
IOC ICG/ITSU
Mosque at Jantang. This mosque was one of the few structures in the
surrounding area that survived the tsunami inundation. Villagers climbed
onto the upper floors to escape wave inundation. Again the concrete open
framework that vented water played a role in allowing the structure to
The amplifying wave can have a curious side effect. Before hitting land,
it draws water from the leading edge, exposing the seafloor for as much
as a mile.
The 1960 tsunami caused major damage in Hilo and killed 61 people.