BYBY

DR.E.ARUMUGAMDR.E.ARUMUGAM

DIRECTORDIRECTOR

CENTRE FOR DISASTER MITIGATION AND CENTRE FOR DISASTER MITIGATION AND MANAGEMENTMANAGEMENT

ANNA UNIVERSITYANNA UNIVERSITY

ELEMENTS OF NATURAL AND MAN-MADE ELEMENTS OF NATURAL AND MAN-MADE DISASTERS AND ITS PREVENTION DISASTERS AND ITS PREVENTION

MEASURESMEASURES

DISASTERS, HAZARDS AND VULNERABILITY

Disasters

What is a disaster?

“…..it a serious disruption of the functioning of a society, causing

widespread human, material, or environmental losses which

exceed the ability of the affected society to cope using its own

resources”.

A disaster is the product of a hazard such as earthquake, flood or

windstorm coinciding with a vulnerable situation which might

include communities, cities or villages.

There are two main components in this definition: hazard and

vulnerability. Without vulnerability or hazard there is no disaster.

Disaster

Relationship between Hazard and Vulnerability

Eg- flood Eg- living in flood prone area

Disaster Risk = Hazard + Vulnerability

Hazard

Vulnera-bility

HazardsDefinition: "Phenomena that pose a threat to people, structures or economic assets and which may cause a disaster. They could be either man-made or naturally occurring in our environment."

Types of Hazards

1. Natural

2. Man-Made

3. Fast Impact

4. Slow Onset

HAZARDS

Floods - Everything located in flood plains. Crops, livestock, machinery, equipment, infrastructure weak buildings, their contents, people. Local economy

Earthquakes - Weak buildings, their occupants and contents. Machinery, equipment, infrastructure

Volcanic Eruptions - Anything close to volcano. Crops, livestock, people, combustible roofs, water supply.

Landslides - Anything located on or at base of steep slopes or cliff tops, roads, and infrastructure, buildings on shallow foundations

Technological disasters - Lives and health of those involved or in the vicinity. Buildings, equipment, infrastructure, crops and livestock. Local economy

Vulnerability

Definition:

" The extent to which a community, structure, service, or

geographic area is likely to be damaged or disrupted by

the impact of particular hazard, on account of their nature,

construction and proximity to hazardous terrain or a

disaster prone area."

This susceptibility to be damaged or affected will

be different to each type of threat and will depend on their

differing characteristics.

Physical VulnerabilityPhysical Vulnerability

• Damage may be caused by earthquakes or floods have been based on the physical location of people.• For example people are only vulnerable to a flood because they live in a flood prone area.

• Depending on construction techniques, materials used, siting and condition, some buildings will be more prone to damage than others depending on the nature of the threat.

Socio-Economic VulnerabilitySocio-Economic Vulnerability The size of a disaster is determined by the event, its effects on

people and their environment, as well as human activities within any society which increase or decrease the potential to be affected.

Types of VulnerabilityTypes of Vulnerability

Physical VulnerabilityPhysical Vulnerability

Socio-economic VulnerabilitySocio-economic Vulnerability

Vulnerability - Choice and RecoveryChoice

Physical vulnerability is as much a function of location and exposure to a hazard as to the physical performance of buildings and structures.

• Due to socio-economic factors some sectors of society will have more choices as to where they live and what assistance they will receive in a disaster.

• Thus it often the case that the poorest are more vulnerable than those who can afford

Recovery• The capacity to recover will depend on income levels, savings, social support systems etc.

THE CYCLE OF DISASTERTHE CYCLE OF DISASTER

• Before a disasterBefore a disaster: - to reduce the potential for human, material, or environmental losses caused by hazards and to ensure that these losses are minimised when disaster strikes

• During a disasterDuring a disaster: to ensure that the needs and provisions of victims are met to alleviate and minimise suffering

• After a disasterAfter a disaster: to achieve rapid and durable recovery which does not reproduce the original vulnerable conditions

BeforeMitigation, preparedness

Disaster !

AfterRelief, rehabilitation,

reconstruction

1. The Disaster Event

2. Recovery

3. Risk Reduction: Mitigation and Preparedness

1. The Disaster Event• The “real-time” event of a hazard occurring and affecting elements at risk.

The duration of the event will depend on the type of threat; ground shaking

may only occur for a matter of seconds during an earthquake whilst flooding

may take place over a longer sustained period.

Disaster Cycle – Three Disaster Cycle – Three StagesStages

2. RecoveryRecovery is used to describe the activities which encompass the three overlapping phases of emergency relief, rehabilitation and reconstruction.

1. Emergency Relief

Refers to the period immediately following the occurrence of a disaster when steps are taken to meet the needs of survivors in respect to shelter, water, food and medical care

2. Rehabilitation

Activities that are undertaken to support the victims’ return to "normal" life and re-integration into regular community functions

3. Reconstruction

Good reconstruction attempts to return communities to improved pre-disaster functioning

3. Risk Reduction: Mitigation and Preparedness

Reducing the risk of disasters involves activities which either reduce or modify the scale and intensity of the threat faced or by improving the conditions of elements at risk.

Risk reduction can take place in two ways:

1. Preparedness

This protective process embraces measures which enable

governments, communities and individuals to respond rapidly to disaster

situations to cope with them effectively.

2. Mitigation

Mitigation embraces all measures taken to reduce both the effect of

the hazard itself and the vulnerable conditions to it in order to reduce the

scale of a future disaster.

• Actors are organized at various levels in the community, in non-

governmental, formal and non‑formal organizations.

• The government is involved through local authorities, national planning bodies and ultimately in the national leadership.

For this reason the actors are identified as:

• Community organizations

• Non-governmental organizations (NGOs)

• Government

ACTORS IN DISASTER MANAGEMENT

1. Community organizations

Local community leadersVoluntary Fire BrigadesCommunity Groups ( youth, women, farmers, self help, etc.)Church/religious organizationsLocal builders/craftsmenHousing Co-operativesPrivate sector: suppliers of materials, equipmentVolunteersSchool teachers

Non Governmental Organizations (NGOs)In recent years, various formal and non‑formal organizations have played an increasingly important role in disaster reduction.

Because of their significant links with grassroots development, these organizations often perform complementary roles with other established organizations.

The role of school teachers, social welfare workers, women’s’ groups, and other socio‑cultural organizations in disaster reduction should not be underestimated.

Religious institutions and their structures have also been involved in a number of ways; for instance in Jamaica hurricane committees are organised on a parish basis.

Immediately after the impact of a disaster, many people look to religious organizations for guidance, emotional support and comfort.

GovernmentGovernment

Local Government And Local Government And Project StaffProject Staff

1.Town or District Architect/Planner2.Town or District Engineer3.Housing Officers4.Building Inspectors5.Contractors6.Public Health Officers7.Medical Staff8.Public and Finance Administrators9.Transport Departments10.Public Utility Staff11.Teachers/Adult educators12.Social (and relief) workers13.Agricultural extension workers14.Information workers/media15.Local Administrators16.Police and Army

National LevelNational Level

1.National Politicians 2.Lawmakers 3.Civil servants 4.Mapping Agencies 5.Development planners 6.Regional Planners 7.University Faculty 8.Research Institutes 9.Employers Associations 10.Professional Organizations11.National Relief Organizations 12.National NGOs 13.Media 14.Bank & Insurance Staff

THE SEQUENCE OF DISASTER MANAGEMENT PLANNING

Disaster management can be divided into pre and post disaster contexts.

The Six stages are:

Inception of disaster planning

Risk assessment

Defining levels of acceptable risk

Preparedness and mitigation planning

Testing the plan

Feedback from lessons learnt

Stage one: Inception of disaster management

Agreed objectives for disaster planning

• Political commitment at all levels of national and local government a

governmental structure with clearly defined authority and an appropriate

budgetary commitment to maintain effective disaster planning up-to-

date, well rehearsed preparedness plans that are comprehensive in

scope and operational at all levels (central, provincial and community).

• These include an emergency management system, ideally the

responsibility of a nominated national co-ordination body mitigation

plans to reduce the hazard threats and vulnerability to them knowledge

of disaster management and specific knowledge of local situations

subject to disaster threats.

Stage two: Risk Assessment

It is a three part process that has to be undertaken in the following sequence:

1. Hazard mapping

Hazard mapping reveals areas which are particularly susceptible to

hazards: earthquake, flood, drought, landslide, etc.

2. Vulnerability analysis

It includes social, economic, natural and physical environmental

factors. Vulnerability analysis is always a 'site-specific' process with

a concern for unique characteristics of a local situation.

3. Resource assessment

When potential losses have been estimated, a further assessment is

needed of the resources or "capacities" existing to improve disaster

planning.

Stage three: Defining levels of acceptable risk

The information gathered through the various processes in Stage Two is then analysed to enable a responsible course of action. Such information may enable NGOs to formulate sustainable development programmes.

Typical questions for decision makers might include:

1. Should they initiate risk reduction measures to protect their citizens or are there other more pressing risks to address such as road safety or AIDS public information programmes?

2. If they decide to proceed with risk reduction against natural hazards what level of protection is required? For example, should shelter be planned or upgraded to resist an earthquake that recurs every 20, 100 or 200 years?

3. Should certain critical elements such as schools and hospitals be given extra levels of safety than say individual dwellings?

4. What is the 'perception of risk' of the affected community and does this differ from official perceptions.

Stage four: Preparedness and Mitigation planning

These actions include measures that are aimed to reduce disaster events in three ways.

1. Through methods to reduce hazard impact, e.g. building flood

protective embankments or walls, creating and managing dam

projects, community grain stores, etc.

2. Through preparedness measures that emphasise short term

activities focused on the emergency period, e.g. emergency flood

reservoirs in drought. Properly done they can reduce loss of life and

property whilst assisting the relief and rehabilitation

3. Through longer term mitigation measures aimed at the reduction of

physical vulnerability, socio economic vulnerability and underlying

causes.

Stage five: testing the plans

• In the representation of Stage Five two ways are indicated to test the

plans that are developed in Stage four.

• One way is through simulation exercises and public drills.

• This approach is obviously a rather inadequate method to determine

whether a preparedness plan or mitigation plan will work or not.

Stage six: feedback from lessons learned

• Information on changes needed in preparedness and mitigation

planning as well as on risk assessment will need to be continuously

passed back to an appropriate stage in the cyclical planning process.

1. The purpose and scope of disaster management

• Disaster management covers all measures that help a society to avoid, minimise loss and recover from hazard impacts.

• These measures include activities which take place before, during and after a disaster event.

• Disaster management therefore incorporates all stages of the disaster cycle which are seen as a continuum and not as discreet and independent components

2. The cyclical sequence of disaster planning

• Disaster management planning is a sequential and continuous process.

• Good planning requires diagnosis, resources, evaluation and feedback towards fulfilling the goal of disaster reduction.

• Because of the wide scope of disaster management and the numerous actors involved it is essential that a framework for co-ordination is accepted and provided for

3. The importance of risk assessment

• Experience indicates that the key component of risk assessment is often omitted or inadequately carried out.

• In many countries disaster planning, incorporating very elaborate preparedness processes, is undertaken with only a vague understanding of the precise nature of hazards, vulnerabilities and resources.

• The result is that much planning is wasted since it relates in a haphazard and inaccurate manner to assumed risks, as opposed to actual threats.

• Thus there is a need for governments to allocate resources for the critical diagnostic process of risk assessment.

DISASTER MITIGATION Definition

“Measures aimed at reducing the impact of a natural or man-made disaster in a nation or community.”

• Disaster mitigation embraces actions taken in advance of a disaster to reduce its effects on a community.

• When used in this sense mitigation includes those actions which are often categorised as being preparedness measures, i.e. preparedness is a part of mitigation.

Distinction between Mitigation and preparedness

• Mitigation refers to long term risk reduction measures which are

intended to minimise the effects of a hazard, for example a dam construction is

considered an activity that mitigates the effects of drought

• Preparedness assumes that certain groups of people or property will

remain vulnerable and that preparedness is necessary to address the

consequences of a hazardous events occurrence. Preparedness is therefore

concerned with measures immediately before and after a hazard event,

e.g. evacuation plans

Mitigation measures

Non Structural Mitigation

Activities and decision making systems which provide the context

within which disaster management and planning operates and is

organised. They include measures such as:

1. Training and education2. Public education3. Evacuation planning 4. Institution building 5. Warning systems

Structural Mitigation

• A typical structural measure is an earthquake resistant building whilst a

typical non structural element is a seismic building code, training and

education, building safety codes, physical measures, land use planning,

public awareness programmes etc.

DISASTER PREPAREDNESS

“Measures which enable governments, organisations, communities and individuals to respond rapidly and effectively to disaster situations. Preparedness measures include the formulation of viable disaster plans, the maintenance of resources and the training of personnel.”

Elements of disaster preparedness

• Taking effective precautionary measures prior to the imminent threat of a disaster

• Improving the emergency response to the effects of a disaster by

organising the delivery of timely and effective rescue and relief

assistance.

Disaster preparedness activities

Risk assessment

The provision and operation of warning systems

Emergency communications and information systems

Maintaining a resource base in anticipation of needs

Public preparedness education and awareness campaigns

Training and drills to ensure maintenance of preparedness levels

Disaster preparedness planning

Risk Assessment:

This information serves as a means to inform decision makers about the need for

disaster preparedness

Communications and early warning systems:

A particular challenge is to ensure that early warnings messages are able to

reach and be understood by those at risk.

Public awareness education:

Those people, communities or organisations who may be at risk ought to be

aware, learn about what to expect and what to do in an emergency

Damage and needs assessment:

following an assessment of damage and level of need must be undertaken by

trained assessment teams in a systematic way in order to determine the

appropriate emergency response and long term recovery

Public awareness and education

Heighten awareness of the disaster threat

Inform about possible pre-earthquake preparedness

measures

Inform about adaptive behaviour both during and

after an earthquake

Encourage the implementation of personal or

organisational preparedness plans and actions

Methods to increase public awareness

Government awareness programmes, deals with disaster awareness or other programmes into which disaster awareness elements could be inserted

National broadcasting systems, radio, T.V and newspapers. Often radio is a crucial means of communication, especially for disparate communities

Organisations, such as the Red Cross

Community level activities, e.g. village meetings, market associations

Maintaining levels of preparedness

Training activities in awareness of disaster risks

Functional and readiness checks

Application of post-disaster reviews

Use of regulations

International assistance liaison

Public awareness activity and use of media publicity, e.g.

disaster awareness days

Education in schools

Drills and simulated exercises

Staff Evacuation Procedures

When evacuation alarm sounds or you are directed to evacuate the facility:1. Remain calm. 2. Shut down all hazardous operations. 3. Follow instructions. 4. Assist disabled persons. 5. Leave the area in an orderly fashion. Close doors, but do not lock. 6. Follow established evacuation routes. 7. Move away from the structure. Go directly to the assembly area (map

provided with plan). Report to the Evacuation Coordinator for a "head count".

8. Do not block the street or driveway. 9. Stay at the assembly area until instructed otherwise.

Fire1. Remain calm.

2. Contact the Fire Department.

3. If the fire is small, try to extinguish it with the proper type of extinguisher or other method. Do not jeopardize personal safety.

4. Do not allow the fire to come between you and the exit.

5. Disconnect electrical equipment if it is on fire and it is safe to do so.

6. Notify the supervisor and evacuation coordinator, if possible.

7. Evacuate if you can not extinguish the fire. Assist disabled persons.

8. Do not break windows.

9. Do not open a hot door. (Before opening a door, touch it near the top. If it is hot or if smoke is visible, do not open.)

10. Do not use elevators.

11. Do not attempt to save possessions.

12. Go directly to the assembly area.

13. Do not return to the affected area until told to by appropriate authorities.

14. Do not spread rumors.

Severe StormsThese first procedures apply to thunderstorms, tornados, hurricanes, etc.

1. Listen to the local radio/TV or NOAA Weather Radio for instructions.

2. Plan ahead before the storm arrives.

3. Tie down loose items located outside or move them indoors.

4. Open windows slightly, time permitting, on the side away from the direction of the storm's approach.

5. Check battery-powered equipment and back-up power sources.

6. Fill vehicles with gas.

In the event of a severe storm warning within the surrounding area:

1. Disconnect electrical equipment and appliances not required for emergency use.

2. Do not use telephone except for an emergency or absolutely essential business.

3. Store drinking water in clean containers (e.g., jugs, bottles, sinks).

4. Avoid structures with wide span roofs (e.g., gymnasium).

5. Otherwise, take cover.

Hurricane Warning1. Board up windows or protect them with storm shutters or tape. Some

should be left slightly open to equalize the pressure. 2. Leave low-lying areas that may be swept by high tides or storm waves. 3. Stay in the building if it is sturdy and on high ground. If not--and

especially if local authorities order an evacuation--move to a designated shelter.

4. Remain indoors. Don't be fooled by the calmness of the "eye." Remember, the winds on the other side of the "eye" will come from the opposite direction.

Hurricane Evacuation1. Follow the instructions of local authorities 2. If transportation is provided by local authorities, use it 3. If you must walk or drive to another location: 4. Leave early enough so as not to be marooned, 5. If driving, ensure there is sufficient gas, 6. Use recommended routes rather than trying to find short-cuts, and 7. Go to a designated location--don't go anywhere else.

FloodIn case of a flood warning in the area:1. Listen to local radio/TV. 2. Prepare to evacuate upon direction. (Note: If a flash flood warning is issued, get out of the

area immediately.) 3. Assist disabled persons and follow instructions of emergency preparedness personnel. 4. Check any battery-powered equipment & back-up power sources. 5. Store drinking water in clean receptacles (e.g., sinks, jugs). 6. Inventory and move to the upper floors emergency supplies such as food, first aid items,

blankets... 7. Secure all loose objects located outside. 8. Assist with protecting objects. 9. Board up windows. 10. Disconnect utilities which are not absolutely essential. 11. Fill vehicle gas tank(s). 12. If driving, know the depth of the water in a dip or low area before crossing. 13. If vehicle stalls, abandon it immediately and seek higher ground. 14. Do not try to cross a stream on foot if water is above your knees. 15. Do not re-enter the affected area until directed by emergency preparedness personnel. 16. Do not spread rumors.

Hazardous Material Accident

Safety Measures1. Evacuate the immediate area. 2. Initiate appropriate first aid and/ or other personnel protection measures, as required. 3. Notify Authorities as soon as possible. 4. Do not re-enter the affected area until directed by the emergency preparedness

personnel. 5. If trained and properly protected, assist with the clean-up operations, as directed. 6. Do not spread rumors.

In case of a hazardous materials accident in the local community:

1. Listen to the local radio/TV. 2. Follow instructions of the emergency preparedness personnel. 3. Evacuate when directed. Follow the designated route to the Assembly Area. 4. Do not re-enter the affected area until directed by emergency preparedness personnel. 5. Do not spread rumors.

EarthquakeDuring The Shaking ---

1. If indoors Stay there. Take cover under sturdy furniture (desks, work tables, etc.) or in a supported doorway. Stay near the center of the building. Do not run for the exit as the stairs may be broken or jammed with people. Do not use elevators. Stay away from glass windows, doors, display cabinets, bookcases, etc. Do not use candles, matches, or other open flame as there may be gas leaks. Extinguish all fires with the proper type of extinguisher or other method.

2. If outdoors Move to an open area away from buildings, utility wires, trees, etc. If forced to stand near a building, watch for falling objects.

3. If driving a vehicle Stop as quickly as safety permits, avoiding overpasses and power lines. Remain in the car until the shaking stops. If able to drive on after the shaking stops, watch for hazards which may have been created by the earthquake.

Explosion

1. Remain calm. 2. Take cover under a table or desk. 3. Be prepared for possible further explosions. 4. Stay away from windows, mirrors, overhead fixtures, filing cabinets,

bookcases, etc. 5. Follow the instructions of the security guards and emergency preparedness

personnel. 6. Evacuate calmly, when directed, to the Assembly Area. Assist disabled

persons. 7. Do not move seriously injured persons, unless they are in immediate danger

(fire, building collapse, etc.) 8. Open doors carefully. Watch for falling objects. 9. Do not use elevators. 10. Avoid using the telephone, except in a life threatening situation. 11. Do not use matches or lighters. 12. Do not re-enter the affected area until directed by emergency preparedness

personnel. 13. Do not spread rumours.

Disaster Preparedness For People With Disabilities

• Check for hazards in the home

During and right after a disaster, ordinary items in the home can cause injury or damage. Anything that can move, fall, break or cause fire is a home hazard. Check for items such as bookcases, hanging pictures, or overhead lights that could fall in an earthquake or a flood and block an escape path.

• Be ready to evacuate

Have a plan for getting out of your home or building (ask your family or friends for assistance, if necessary). Also, plan two evacuation routes because some roads may be closed or blocked in a disaster.

Maintain a list of the following important items

Special equipment and supplies, e.g.,hearing aid batteries Current prescriptions names and dosages Names, addresses, and telephone numbers of doctors and pharmacist Detailed information about the specifications of your medication regime Create a self-help network of relatives, friends or co-workers to assist in an emergency.

• Flashlight with extra batteries.

• Portable, battery-operated radio and extra batteries.

• First aid kit and manual.

• Emergency food and water.

• Non-electric can opener.

• Essential medicines

• Cash and credit cards

• Sturdy shoes.

Disaster supplies to be on hand

Risk assessment

Risk assessment therefore has two central components:

Hazard analysis, understanding the scale, nature and characteristics of a hazard

Vulnerability analysis, the measuring of the extent to which people or buildings are likely to suffer from a hazard occurrence.

"A process of analysis to identify and measure risks from natural hazards that affect people, property and the environment. This process can also encompass the assessment of available resources to address the risks."

Resource Base: Based on Risk assessment and in particular

vulnerability analysis, specific requirements in terms of materials and people involved as well as costs should be made explicit and planned forEmergency disaster services: following damage and need assessments, relief provisions must be secured and emergency services made operable from all available sources including the international community. Maintenance of levels of preparedness: all plans should be rehearsed in order to maintain preparedness levels and improve response in the event of a real disaster.

Conducting risk assessment The process of risk assessment is usually conducted in the following sequence:

Hazard analysis: Hazard information is needed on such matters as location,

frequency, duration and severity of each hazard type.

Vulnerability analysis: Vulnerability analysis starts with creating an

inventory of all elements that are 'at risk' to the identified hazards such as

social groups, buildings, infrastructure, economic assets, agriculture etc.

Risk Evaluation and determining levels of acceptable risk: Once data on

the nature of the hazards and vulnerability has been collected, synthesised

and analysed by technical staff in the categories noted above it.

Vulnerability assessment “The analysis of the vulnerability of various sectors that are exposed

to the natural hazards identified in the hazard analysis exercises.

The sectors include social, livelihoods, economic, physical assets,

agriculture, political and administration.”

The Earthquake

WHAT CAUSES EARTHQUAKE

Rocks are made of elastic material, and so elastic strain energy is stored in them during the deformations that occur due to the gigantic tectonic plate actions that occur in the Earth. But, the material contained in rocks is also very brittle.

Thus, when the rocks along a weak region in the

Earth’s Crust reach their strength, a sudden

movement takes place there opposite sides of the

fault (a crack in the rocks where movement has taken

place) suddenly slip and release the large elastic

strain energy stored in the interface rocks.

For example, the energy released during the 2001 Bhuj (India)

earthquake is about 400 times (or more) that released by the 1945 Atom

Bomb dropped on Hiroshima!!

Types of Earthquakes

i. Inter-plate Earthquakes

Most earthquakes in the world occur along the

boundaries of the tectonic plates and are called

Inter-plate Earthquakes (e.g., 1897 Assam (India)

earthquake).

ii. Intra-plate Earthquakes

A number of earthquakes also occur within the plate

itself away from the plate boundaries (e.g., 1993

Latur(India) earthquake); these are called Intra-plate

Earthquakes.

In both the slip generated at the fault during earthquakes is along both vertical and horizontal directions (called Dip Slip) types of earthquakes, and lateral directions (called Strike Slip) (Figure), with one of them dominating sometimes.

TYPES OF FAULTS

Dip Slip

Strike Slip

How the ground shakes?

• Large strain energy released during an earthquake travels as seismic waves in all directions through the Earth’s layers, reflecting and refracting at each interface.

• The instrument that measures earthquake shaking, a seismograph, has three components – the sensor, the recorder and the timer.

The motion of the ground can be described in terms of displacement, velocity or acceleration. The variation of ground acceleration with time recorded at a point on ground during an earthquake is called an accelerogram.

Characteristics of Strong Ground Motions

Terminology

•The point above the focus on the surface of earth is called the Epicenter

• The point where energy is released is called the Focal Depth

Magnitude

The magnitude of an earthquake is a measure of the amount of energy released. It is a quantitative measure of the actual size of the earthquake.

Each earthquake has a unique magnitude assigned to it.

This is based on the amplitude of seismic waves measured at a number of seismograph sites, after being corrected for distance from the earthquake.

Magnitude estimates often change by up to 0.2 units, as additional data are included in the estimate.

Intensity

Intensity is a qualitative measure of the actual shaking at a location during an earthquake, and is assigned as Roman Capital Numerals.

The distribution of intensity at different places during an earthquake is shown graphically using isoseismals, lines joining places with equal seismic intensity

Seismic Zones in India

The national Seismic Zone Map presents a large-scale view of the seismic zones in the country. Local variations in soil type and geology cannot be represented at that scale. for the purposes of urban planning, metropolitan areas are microzoned. Seismic microzonation accounts for local variations in geology, local soil profile, etc,.

Richter Scale

The Richter scale is logarithmic, that is an increase of 1 magnitude unit represents a factor of ten times in amplitude.

The seismic waves of a magnitude 6 earthquake are 10 times greater in amplitude than those of a magnitude 5 earthquake.

However, in terms of energy release, a magnitude 6 earthquake is about 31 times greater than a magnitude 5.

MagnitudeM=1 to 3: Recorded on local seismographs, but generally not felt

M=3 to 4: Often felt, no damage

M=5: Felt widely, slight damage near epicentre

M=6: Damage to poorly constructed buildings and other structures within 10's km

M=7: "Major" earthquake, causes serious damage up to ~100 km (recent Taiwan, Turkey, Kobe, Japan, and California earthquakes).

M=8: "Great" earthquake, great destruction, loss of life over several 100 km (1906 San Francisco, 1949 Queen Charlotte Islands) .

M=9: Rare great earthquake, major damage over a large region over 1000 km (Chile 1960, Alaska 1964, and west coast of British Columbia, Washington, Oregon, 1700).

Some Past Earthquakes in India

The timing of the earthquake during the day and during the year critically determines the number of casualties. Casualties are expected to be high for earthquakes that strike during cold winter nights, when most of the population is indoors.

Earthquake causes shaking of the ground. So a building resting on it will experience motion at its base.

Inertia Forces in Structures

Seismic Effects on Structures

Importance of Architectural Features

Simple Plan shape buildings do well during earthquakes

EARTHQUAKE RESISTANCE

2. Vertical reinforcement required in masonry buildings

1. Horizontal Bands in Masonry Building improve Earthquake resistance

VERTICAL REINFORCEMENT HELPS