and tsunami disaster mechanism of tsunami and tsunami...
TRANSCRIPT
Tokyo Institute of Technology
Jan.10 and 24,2014
Earthquake and Tsunami Disaster Reduction
1.2011Great East Japan Earthquake
and Tsunami Disaster
2.Mechanism of Tsunami
and Tsunami Disaster Mitigation
Shigeo TAKAHASHI
Port and Airport Research Institute, Japan
Visiting Professor , Tokyo Institute of Technology
Tokyo Institute of Technology FS2011
Feb.2013
Earthquake and Tsunami Disaster Reduction
Contents
2.Mechanism of Tsunami
and Tsunami Disaster Mitigation
2.1.Mechanism of Tsunami
2.2. Tsunami Damages
2.3.Tsunami Disaster Mitigation
2.1.Mechanism of Tsunami
@Tsunami Generation
@Tsunami Propagation
@ Tsunami Run-up
As an engineer it is very important
to understand the basics of tsunami
mechanism in this chapter.
Tsunami is a very long wave
and therefore, very powerful
• Tsunami has many characteristics
as a wave.
• Tsunami has many characteristics
as a flooding current
A simplified Model of sea bottom displacement and Initial Tsunami
Vertical displacement of Seabottom =Initial Tsunami Profile
Generation of Tsunami
Propagation toward shore side and ocean side
How high is the tsunami height moving toward the
shore?
Propagation of Tsunami
@Seismic Activity (Earthquake)
Movement of Fault in seabottom
Subduction Zone Earthquake
@ Landslide
@ Eruption of Volcano
Causes of Deformation of Sea bottom
to generate tsunami
Philippine Pl.
Pacific Pl.
Indo-Australia Pl.
North American Pl.
Eurasia Pl.
African Pl.
South American Pl.
Antarctic Pl.
Epicenters of Large Earthquakes Earth-Plates Boundaries and Subduction Zones
12
Earthquake and Tsunami Generation(1/2) Movement of Techtonic Plates at Subduction zone
Continental Plate Ocean Plate
(Subducting Plate)
Deformation of the Continental Plate is increased by the
Subducting Plate.
13
Earthquake and Tsunami Generation(2/2)
Ocean Plate
tsunami
tsunami tsunami
The deformation is released suddenly by rupture which causes an
earthquake. The sea bottom deformation causes the tsunami.
The tsunami profile is equal to the sea bottom deformation
Rupture/
Earthquake
A simplified Model of
Initial Tsunami
Vertically and horizontally distorted Picture
Near the subduction zone the water depth is 1 to 5km
and the height is only less than 10m.
Also the wave length is 100 to 200 km for example.
Wind Wave
Tsunami
Storm Surge
Tide
Tsunami = Very Long Wave
(period 10mins to 1hr)
Water Waves
(Water Surface Wave/Gravity Waves)
Gravity wave theory
( From 19th century)
Understanding of the characteristics
Development of Water Wave Theory
Numerical simulation of Water waves
(From 20th Century)
Now we can calculate Tsunami generation,
propagation and run-up.
Speed of Tsunami C=(gh)*0.5
Velocity of Water Particles U=(η/h) ・ C
Basics of Long Waves from wave theory
(Basic characteristics of tsunami)
Continuity of Wave Power
η2C=ηo2Co
Height of Tsunami η=ηo・ (Co/C)*0.5
=ηo (ho/h)*0.25
Breaking
Wave
U=10m/s
x=3000m
U=2.7m/s
x=770m
U=0.025m/s
x=7m
Velocity U and Displacement X of
Water Particles; U=(H/2h)*C
Increase of tsunami height due to
Geographical features of coasts
V-shape bay
By contraction
Cape
By Refraction
Behind island
By Diffraction
Tsunami at Sendai Plain
NHK Special “The Great Eastern Japan Earthquake”
by NHK (Japan Broadcasting Corporation) on May 7, 2011.
Special feature of tsunami front in coasts. Soliton Fission (Split) and Breaking of Tsunami Front
The behavior of tsunami front near the coasts is
very important especially to understand the
mechanism of failures of coastal defenses.
Tsunami front with Soliton Fission at a water depth 30m
NHK Special “The Great Eastern Japan Earthquake”
by NHK (Japan Broadcasting Corporation) on May 7, 2011.
Tsunami at Kuji (Breaking wave front)
NHK Special “The Great Eastern Japan Earthquake”
by NHK (Japan Broadcasting Corporation) on May 7, 2011.
Summary of Tsunami Generation,
Propagation and Run-up 1.Tsunami is a long and powerful wave.
2.Deformation of sea bottom generates tsunami.
3.Tsunami propagates with the speed of Root gh.
The tsunami speed is very large in deep water like
airplane. But it becomes slow near coasts like cars.
4.Tsunami increases the height as the water depth
decreases. In the coasts it becomes several times.
5.Due to reflection and refraction tsunami attack the
coasts many times.
Summary of Tsunami Generation and
Propagation
6.Due to the coastal geographical features incident
tsunami height varies significantly.
7.The run-up of the tsunami into shore and land is
very different depending on the topography.
8. Tsunami intrudes into land from rivers and coasts
in addition to ports.
9. Tsunami front is very dangerous due to breaking.
2.2. Tsunami Damages
@ Recent Tsunami Disasters
Results of field surveys
@ Recent Studies on Tsunami Damages
Experiments on tsunami damages
@ Summary of Tsunami Damages
We believe that disaster prevention starts from
understanding of disaster by people.
We have to know what will actually occur by
tsunami. We need to prepare for Disaster
Scenario to let people know.
We can learn from actual disasters.
We conducted many field surveys in Japan and in
the world.
Field Surveys of Tsunami
Talchuano, Chilean Earthquake and Tsunami,
Feb.27,2010
Tsunami height 7~8m 680 Containers were drifted toward the town and then 30% of them moved toward the sea.
Photo: The International Federation of Red Cross and Red Crescent Societies
11
Talchuano, Chilean Earthquake and Tsunami,
Feb. 27,2010
Photo: The International Federation of Red Cross and Red Crescent Societies
11
Dichato, Chilean Earthquake and Tsunami
Feb. 27,2010
Photo: The International Federation of Red Cross and Red Crescent Societies
11
Dichato Chilean Earthquake and Tsunami Feb. 27,2010
Photo: The International Federation of Red Cross and Red Crescent Societies
11
@Heavy
damage in low-
lying area near
a river
@only 18 dead
among 4000
residents
01
234
56
78
0 50 100 150 200 250 300 350 400 450 500
Magnitude of Earthquake and Tsunami
M7
limited Local Tsunami
M8
Large Regional Tsunami
M9
Huge Ocean Tsunami
Frequency of Tsunami Disasters
Tsunami repeats with a frequency of 100 years or more in the
same area.
In Japan:
Major tsunami disasters occur once for ten years.
Devastating tsunami disasters occur once for hundred years.
In the world:
Major tsunami disaster occurs almost for one or two years.
Devastating disaster occurs once for ten or twenty years.
Tsunami Disasters Place Casualties
2011 Tōhoku Earthquake and Tsunami Japan 20,000
2004 Indian Ocean Tsunami Indonesia 220,0000
1908 Messina Earthquake (Landslide) Italy 70,000
1896 Meiji-Sanriku Earthquake Japan 22,000
1883 Eruption of Krakatoa Indonesia 36,000
1868 Arica Earthquake Chile 25,000
1792 Unzen Eruption and Earthquake
(Landslide tsunami) Japan 10,000
1771 Great Yaeyama Tsunami Japan 13,000
1755 Lisbon Earthquake and Tsunami Portugal 100,000
1707 Hōei Earthquake and Tsunami Japan 30,000
Summary of Major Tsunami Disasters
Experimental studies on tsunami damage
Prototype Experiments in Large Hydro-Geo Channel to
investigate tsunami damages
Relation between Tsunami Damage and
Tsunami Height - Imamura/Iida (modified)
Tsunami Height Damage 0.5m No damage 2m Damage in Coasts and ships 4-6m Severe Inundation and casualty 10m- Devastating Damage even in the places far from coast
10m Tsunami Causes
all the damages due to
tsunami.
It destroyed everything
in the town including
coastal defenses.
Destruction and washed-away of houses
Drift and crash of cars
Fires
Destruction of tanks and oil spill
Destruction of Railways, roads andbridges
subsidance of ground
Inundation of rice paddles
Drifting and collision of ships
Destruction and inundation of portfaciliteis
Drifting and collision of timbers andcontainers
Debris deposit in ports
Scouring and deposit in ports
Scouring of sandy beaches anddestruction of green belts
Destruction of acuaculture facilities
Scouring and sliding of Breakwaters andquaywalls
Destruction of jetties and detachedbreakwatersDestruction (scouring) of Dykes andSeawallsDestruction of water gates
Gene
ral
Port
s an
d Co
asts
Coa
stal
Def
ense
s
10m tsunami
damage
Difference of Water Level (Sliding of Wall)
Rapid Current (Scattering and Scouring)
Wave Impact (Seawall Failure
Rapid Current (Seawall Scouring and Overturning)
Typical Damages to Tsunami Defenses
Summary of Tsunami Damages
1. Generally, Tsunami attacks the lower areas near coasts. 2. Even by a small tsunami, people might be killed, cars are floated, and wooden houses are damaged. 3. Huge tsunami destroys all the town including coastal defenses.
Summary of Tsunami Damages 4. Ships and other floated objects causes the secondary damages. 5. Fire can always occur and cause significant the secondary damages. 6. Receding current is very strong and carries the floated objects into sea. 7. Concrete buildings are relatively strong. 8. Number of Casualties depend on the number of inundated houses. However, it deeply depends on the evacuation rate.
3.Tsunami Disaster Mitigation
@non-structural countermeasures
@ Structural countermeasures
We need to improve our preparedness by non-
structural and structural countermeasures.
We have to improve our town to be
resilient to Tsunami disaster.
Reduce the casualties into zero
Resilient town
= Ensure early recovery
= Reduce damage
Improvement of Preparedness
What is the most significant difference
between Earthquake and Tsunami
Attacks?
We can have a time for evacuation against tsunami attack !
We can reduce the casualty by tsunami into zero by proper evacuation.
TIME
Non-structural Countermeasures
1.Effective Evacuation
@Tsunami Warning System
@ Hazard Map
@ Evacuation Facilities(Building,Tower etc)
2.Dissemination of Tsunami Knowledge
3. Land Usage Planning
• Casualties vs Population in inundated area
• Huge Tsunami without Early Warning
1896 Meiji Sanriku Tsunami 22000/72500=30%
Indian Ocean Tsunami (Banda Ache) 79000/140000=56%
• Huge Tsunami with Warning
2011 Great East Japan Tsunami 19000/620000=3%
• Medium Tsunami with Warning
1983 Nihonkai-Chubu Tsunami 104/9900= 1%
We can reduce the casualties less than 1%, zero!
Evacuation with proper warning is very important!
Tsunami Warning System
• Warning
– Warning=Large Tsunami(3,4,6,8,10m above)
– Tsunami (1,2m) – Caution=0.5m
• Local Earthquake Tsunami(1954) • □ New system (1999) JMA • Tsunami Database • (100,000 Calculated Tsunamis) • Within 3 min. • Distant Earthquake Tsunami(1960) • □ International Cooperation • Tsunami Early Warning System
Improvement of Tsunami Warning
For 2011 tsunami, the early warning was not so
accurate. To issue the warning within 3 minute
the predicted tsunami was not large enough
• More accurate tsunami Prediction
• Offshore Tsunami Observation
• Real-time Tsunami Prediction using the
observed offshore tsunami data.
Plan of Underwater Cable Network for
Earthquake and Tsunami observation.
National Research Institute
for Earth science and
Disaster Prevention
Underwater Seismometer
sand Pressure Meters with
cable net works
Improvement of Evacuation Methods
Evacuation Buildings
High Lands and Evacuation Towers
Tsunami Evacuation
= Vertical Evacuation
2011 Great East Japan earthquake and Tsunami Disaster
Evacuation places were not so close to people.
Many people encountered Tsunami during long evacuation
Many people used cars and involved in traffic jams.
Improvement of Evacuation
Not Horizontal but Vertical Evacuation
5 Minutes Evacuation by Emergency Refuge using High Buildings
Modern concrete
buildings were
inundated but
remained.
Other measures for safe evacuation
Seminars and Lectures for disaster education
Transmission of tsunami experience
Installation of Evacuation sign boards
Improvement of evacuation places
Improvement of evacuation routes
Preparation of evacuation building
88
沿岸部低地での
津波防災まちづくり(イメージ)
Resilient Coastal Towns
Disaster reduction (mitigation) to ensure early recovery
Compact Coastal Towns by House Relocation into high lands
and High Buildings near Coasts
Not only earthquake and tsunami we have typhoons and
therefore storm surges and waves in the coasts.
In 1959 we had ISEWAN Typhoon which killed 5000
people
We are preparing for coastal disasters under
Seacoast Acts and Disaster Prevention Acts
from 1950’s.
Laws for Coastal Disaster Prevention
History of Disaster Prevention Acts
・In 1961Disaster Countermeasures Basic Act ・In 1962 Act concerning special financial support to
deal with the designated disaster of extreme severity
In 1962 Establishment of Central Disaster Management Council
In 1963 Formulation of Basic Disaster Management Plan
・In 1972, Act concerning special financial support for
promoting group relocation for disaster mitigation
History of Disaster Prevention Acts
In 1978, Large Scale Earthquake Countermeasure Special Act
( Basic plan for earthquake disaster prevention) @Definition of jurisdictions and responsibilities for
disaster management @Disaster management system and plan @Disaster preparedness @Emergency actions and recovery @Financial measure @State of emergency
Structural Countermeasures
Tsunami Seawalls Tsunami Dike Tsunami Breakwater Tsunami Gate Artificial High Ground
Houei Nankai
1707
Ansei Nankai
1854
Showa
Nankai 1946
Tsunami Dike by
Hamaguchi
Hiro Village 1855-
1857
From HP of Hirokawa-Town
Land use planning in Aonae District
Tsunami Countermeasures (Aonae District)
New Town
Park
ReclamationSeawall
Completed tsunami mitigation works
In Aonae Fishery Port Area
Artificial High Ground11m seawall
6m Seawall
Fishery Port
Tsunami Risk Assessment
Risk=Hazard x Vulnerability
Vulnerability = Ground Height
Population
Economic Activities
Preparedness
Scenario based risk assessment
Disaster Scenarios of
@Earthquake /Tsunami
@Warning and Evacuation
@Inundation/Damages/Secondary Damage
@Rescue
@Recovery
First, we should write a disaster scenario
(what will actually occur) if we have Level 1
tsunami or Level 2 tsunami now.
Based on the disaster scenarios we
have to improve preparedness using
various structural and non-structural
counter measures gradually.
We always need to know what is the
weakest point for tsunami in each town.
Improvement of preparedness
1. The primary objective of disaster management is to
save human lives. Additionally, disaster management is
critical for mitigating damages to property and society
especially from tsunamis and storm surges. Providing the
most effective prevention and management demands that
governments use the best existing technology and science
available. All countries in the Asia-Pacific region are
affected by tsunamis and storm surges and they should
work together through international cooperation and
collaboration to provide the best disaster management and
risk mitigation possible with existing technology and science.
Summary of the 4th International Workshop on Coastal Disaster
Prevention (Direction of tsunami disaster mitigation)
2. Although basic tools for disaster management are
available, it is imperative that we, researchers,
scientists and engineers, should develop more
advanced technology, not only to reduce the
casualties but to maintain the people’s activities (to
continue their business activities) more effectively
and economically. Prediction is key to the effec-
tive evacuation and prevention of losses.
International cooperation and collabora-tion
including sociologists are needed to develop and
use the technology effectively.
Summary of the 4th International Workshop on Coastal Disaster
Prevention (Direction of tsunami disaster mitigation)
3. To provide the best service to the people of the
Asia-Pacific region, we need to enhance disaster
preparedness with holistic and resilient disaster
mitigation measures. It is no longer acceptable to
consider disaster management on a local scale, our
vision must extend across the horizon. Solutions to
mitigation must be resilient and robust. Participation
by people is fundamental to effective disaster
preparedness and post-disaster management.
Dissemination of the knowledge and cooperation with
people at all levels is especially important.
Summary of the 4th International Workshop on Coastal Disaster
Prevention (Direction of tsunami disaster mitigation)
The seas are beautiful and rich.
Coastal Disaster Mitigation with
our wisdom and modern technology
Live together with Rich but Violent Seas
Please write one page report on tsunami disaster.
The title should be
Improvement of Tsunami Preparedness in your
country.
Your report should be submitted before Jan. 31.
Email : [email protected]
Assignment