Earthquake Risk Reduction 1- Concepts

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Earthquake Risk Reduction 1- Concepts
Terminology
Charles SCAWTHORN Junji KIYONO Kyoto University

1. Concepts and Terminology
2. Hazard, Vulnerability Risk Assessment
3. Mitigation and ERR Program Development

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Earthquakes cause death and destruction

• Earthquake Killed
• 2005 South Asia 80,000
• 2004 Indian Ocean Tsunami 283,000
• 2003 Bam, Iran 31,000
• 1988 Spitak, Armenia 25,000
• 2001 Gujarat, India 20,000
• 1999 Izmit-Duzce, Turkey 17,000
• 1993 Latur-Killari, India 9,700
• 1995 Kobe, Japan 6,600
• 1999 Chi-Chi, Taiwan 2,400
• 1990 Philippines (N Luzon) 1,620
• 1976 Philippines (Mindanao) 8,000

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Key Words

• Plate Tectonics
• Subduction
• Fault (ie, 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
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Agents of Damage -1
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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
  earths 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 collapseMw 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 earthquakes 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)
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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
damage
Statistical approach
MMI
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Seismic Vulnerability-3
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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 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.

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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
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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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Earthquake Risk Reduction Presentations

1. Concepts and Terminology
2. Hazard, Vulnerability Risk Assessment
3. Mitigation and ERR Program Development