Earthquake Risk Reduction Concepts & Terminology

Session 1 World Bank Institute

Charles SCAWTHORN Junji KIYONO Kyoto University Earthquake Risk Reduction

Earthquakes Cause Death and Destruction

Earthquake  2005 South Asia  2004 Indian Ocean Tsunami  2003 Bam, Iran  1988 Spitak, Armenia  2001 Gujarat, India  1999 Izmit-Duzce, Turkey  1993 Latur-Killari, India  1995 Kobe, Japan  1999 Chi-Chi, Taiwan  1990 Philippines (N Luzon)  1976 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

Key Words

Plate Tectonics, Subduction, Fault (i.e. Earthquake Fault), Seismotectonics, Magnitude, Intensity, Vulnerability, Risk Management Earthquake Risk Reduction 3

Plate Tectonics and Earthquakes - 1

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Plate Tectonics and Earthquakes - 2

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Seismogenesis

Interslab EQs Hot Spot Crustal EQs Intraslab EQs Earthquake Risk Reduction 6

Agents of Damage -1

landslide tsunami shaking faulting liquefaction fire faulting Earthquake Risk Reduction 7

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

M w

, or ‘

moment’ magnitude

scale. M w M w 6 earthquakes are damaging and some buildings may collapse; 7 are very damaging, and many buildings may collapse; M w 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. Earthquake Risk Reduction 8

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. Earthquake Risk Reduction 9

PHIVOLCS Earthquake Intensity Scale (abbrev)

Intensity Scale I II III IV V VI VII VIII IX X Description Scarcely Perceptible Slightly Felt

- Felt by few individuals at rest indoors. Hanging objects swing slightly. Still Water in containers oscillates noticeably.

Weak

- Felt by many people indoors especially in upper floors of buildings …Still water in containers oscillates moderately.

Moderately Strong

- Felt generally by people indoors and by some people outdoors. Light sleepers are awakened.

Strong

- Generally felt by most people indoors and outdoors. Many sleeping people are awakened.

Very Strong

- Many people are frightened; run outdoors. Some people lose their balance. Very old or poorly built houses and man made structures are slightly damaged though well-built structures are not affected.

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.

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.

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.

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 Earthquake Risk Reduction 11

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. Earthquake Risk Reduction 13

Seismic Vulnerability - 3

Two approaches: Detailed engineering model F = [K] X  Sa % damage Statistical approach MMI Earthquake Risk Reduction 14

Seismic Vulnerability-3

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 4 Wood Frame RC Shear Wall URM 6 8

Earthquake Risk Reduction

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… Loss – human injury, cost or repairs, business interruption, social disruption… Built Environment – buildings, industry, infrastructure… Human Environment – People, organizations, institutions, cultural heritage, finances… Earthquake Risk Reduction 16

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

Earthquake Risk Reduction Session 2 Session 3 18

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. Earthquake Risk Reduction 19