Comprehensive Disaster Risk Management: Concept & Terminology

Report
Earthquake Risk Reduction
Concepts & Terminology
Session 1
World Bank Institute
Charles SCAWTHORN
Junji KIYONO
Kyoto University
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Earthquakes Cause Death and
Destruction
Earthquake
 2005 South Asia
 2004
 2003
 1988
 2001
 1999
 1993
 1995
 1999
 1990
 1976
Indian Ocean Tsunami
Bam, Iran
Spitak, Armenia
Gujarat, India
Izmit-Duzce, Turkey
Latur-Killari, India
Kobe, Japan
Chi-Chi, Taiwan
Philippines (N Luzon)
Philippines (Mindanao)
Earthquake Risk Reduction
Killed
80,000
283,000
31,000
25,000
20,000
17,000
9,700
6,600
2,400
1,620
8,000
2
Key Words
Plate Tectonics, Subduction, Fault (i.e. Earthquake Fault), Seismotectonics,
Magnitude, Intensity, Vulnerability, Risk Management
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Plate Tectonics and Earthquakes - 1
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Plate Tectonics and Earthquakes - 2
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Seismogenesis
Interslab
EQs
Crustal EQs
Intraslab
EQs
Hot Spot
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Agents of Damage -1
landslide
tsunami
shaking
liquefaction
faulting
fire
faulting
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Measuring Earthquakes
 Earthquakes are measured by instruments termed Seismometers,
which measure how the ground moves.
 Data from several measurements can be used to ‘triangulate’
where the earthquake began to release energy – the corresponding
point on the earth’s surface is called the epicenter’
 The more the ground moves, the greater the energy release. The
total energy released by an earthquake is estimated from several
instruments, and used to calculate the “magnitude”, or overall size, of
an earthquake – the most common magnitude scale is Mw, or
‘moment’ magnitude scale.
 Mw 6 earthquakes are damaging and some buildings may collapse;
Mw 7 are very damaging, and many buildings may collapse;
Mw 8 and larger are extremely damaging, and very many buildings
may collapse. In the same way, landslides, liquefaction and other
agents of damage are worse, the larger the magnitude.
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Seismic Intensity and Hazard
 While magnitude measures the overall size of an earthquake,
the earthquake’s effects (or intensity) vary from point to point.
In general, the closer to the epicenter, the stronger the intensity.
 Intensity is measured using many scales – including the PHIVOLCS
Scale (PEIS), Modified Mercalli Intensity (MMI), MSK, European
Macroseismic (EMS), and Japan Meterological Agency (JMA) scales.
The PEIS varies from 0 to 10, while the MMI, MSK and EMS are all
similar and vary from 0 to 12.
 Generally, on the MMI, MSK and/or EMS scales:
 6 is the start of damage;
 8 is significant damage with some collapsed buildings;
 10 is very serious damage, with perhaps many collapsed
buildings
 12 is total damage
 Seismic hazard refers to the likelihood of occurrence of earthquake
effects, and is measured in the probability of intensity (or more
technical measures) during a period, such as the next 100 years.
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PHIVOLCS Earthquake Intensity Scale
(abbrev)
Intensity
Scale
Description
I
Scarcely Perceptible
II
Slightly Felt - Felt by few individuals at rest indoors. Hanging objects swing slightly. Still Water in containers oscillates noticeably.
III
Weak - Felt by many people indoors especially in upper floors of buildings…Still water in containers oscillates moderately.
IV
Moderately Strong - Felt generally by people indoors and by some people outdoors. Light sleepers are awakened.
V
Strong - Generally felt by most people indoors and outdoors. Many sleeping people are awakened.
VI
Very Strong - Many people are frightened; run outdoors. Some people lose their balance. Very old or poorly built houses and manmade structures are slightly damaged though well-built structures are not affected.
VII
Destructive - Most people frightened and run outdoors. Old or poorly-built structures suffer considerably damage. Some well-built
structures are slightly damaged. Limited liquefaction, lateral spreading and landslides are observed.
VIII
Very Destructive - People panicky. People find it difficult to stand even outdoors. Many well-built buildings are considerably
damaged. Water and sewer pipes may be bent, twisted or broken. Liquefaction and lateral spreading cause man- made structure to
sink, tilt or topple. Numerous landslides and rockfalls occur in mountainous and hilly areas. Boulders are thrown out from their
positions particularly near the epicenter. Fissures and faults rapture may be observed. Trees are violently shaken.
IX
Devastating - People forcibly thrown to ground. Many cry and shake with fear. Most buildings are totally damaged. bridges and
elevated concrete structures are toppled or destroyed. Water sewer pipes are bent, twisted or broken. Landslides and liquefaction
with lateral spreadings and sandboils are widespread. the ground is distorted into undulations. Trees are shaken very violently with
some toppled or broken. Boulders are commonly thrown out. River water splashes violently on slops over dikes and banks.
X
Completely Devastating - Practically all man-made structures are destroyed. Massive landslides and liquefaction, large scale
subsidence and uplifting of land forms and many ground fissures are observed. Changes in river courses and destructive seiches in
large lakes occur. Many trees are toppled, broken and uprooted.
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MMI Scale
I. People do not feel any Earth movement.
II. A few people might notice movement if they are at rest and/or on the upper floors of tall buildings.
III. Many people indoors feel movement. Hanging objects swing back and forth. People outdoors might
not realize that an earthquake is occurring.
IV. Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors rattle. The
earthquake feels like a heavy truck hitting the walls. A few people outdoors may feel movement. Parked cars rock.
V. Almost everyone feels movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken.
Pictures on the wall move. Small objects move or are turned over. Trees might shake. Liquids might spill out of
open containers.
VI. Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture
moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No
structural damage.
VII. People have difficulty standing. Drivers feel their cars shaking. Some furniture breaks. Loose bricks fall from
buildings. Damage is slight to moderate in well-built buildings; considerable in poorly built buildings.
VIII. Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures
such as towers and chimneys might twist and fall. Well-built buildings suffer slight damage. Poorly built structures
suffer severe damage. Tree branches break. Hillsides might crack if the ground is wet. Water levels in wells might
change.
IX. Well-built buildings suffer considerable damage. Houses that are not bolted down move off their foundations. Some
underground pipes are broken. The ground cracks. Reservoirs suffer serious damage.
X. Most buildings and their foundations are destroyed. Some bridges are destroyed. Dams are seriously damaged.
Large landslides occur. Water is thrown on the banks of canals, rivers, lakes. The ground cracks in large areas.
Railroad tracks are bent slightly.
XI. Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground. Underground pipelines
are destroyed. Railroad tracks are badly bent.
XII. Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large
amounts of rock may move
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Seismic Vulnerability - 1
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Seismic Vulnerability - 2
 Seismic Vulnerability is the degree of damage or loss
caused by a given level of seismic intensity.
 Seismic vulnerability depends on the materials, age,
condition and structural layout of a building or other
structure.
 Weak brittle materials, such as adobe, unreinforced
masonry, and older reinforced concrete buildings,
are very likely to be damaged in an earthquake
- they have high vulnerability.
 Steel, wood and newer reinforced concrete buildings
are less likely to be damaged in an earthquake
- they have low vulnerability.
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Seismic Vulnerability - 3
Two approaches:
Detailed engineering model

F = [K] X
Sa
% damage
Statistical approach
MMI
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Damage
Seismic Vulnerability-3
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Wood Frame
RC Shear Wall
URM
4
6
8
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MMI
10
12
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Earthquake Risk
 Assets may be people, property,
profits, or other things of value.
 Loss is the reduction in value of
an asset due to damage. Loss is
measured in many ways, such as
the ratio of fatalities to total
population, repair cost ratio, etc.
 Risk is the uncertainty of loss.
 Risk or Loss estimation is the
quantification of the earthquake
loss, and is a basic first step in
managing earthquake risk.
Earthquake Effects –
faulting, shaking
intensity, liquefaction,
tsunami…
Earthquake Risk Reduction
Built Environment –
buildings, industry,
infrastructure…
Human Environment –
People, organizations,
institutions, cultural
heritage, finances…
Loss – human
injury, cost or
repairs, business
interruption, social
disruption…
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Earthquake Risk Reduction
 Earthquake damage and loss can
be reduced or mitigated in a
number of ways.
 Mitigation is possible at each
step of the earthquake loss
process.
 Breaking the chain of the
causation of earthquake damage
anywhere reduces or eliminate
the loss.
 The earlier in the process the
chain is broken, the more
effective is the mitigation.
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Earthquake Risk Reduction Program
Session 2
Session 3
Earthquake Risk Reduction
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Earthquake Risk Reduction
 The goal of Earthquake Risk Reduction is not to find a solution,
but rather to find the best solution. “best” implies decision-making.
 Decision-making consists of two basic steps;
 Estimate the risk, and
 Examine mitigation alternatives.
 Estimating the risk involves defining the problem, quantifying the
current risk (ie, as-is), and determining if further action is needed.
 Examining mitigation alternatives requires selecting the basis for
analysis, identifying alternatives, screening alternatives, and
choosing a decision method.
 The last step in Earthquake Risk Reduction is implementing the
alternatives. An earthquake risk management program consists
of the following steps; funding, program management,
implementing the plan, risk transfer and an emergency plan.
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