DISASTER MANAGEMENT

EARTHQUAKES

Definition and Measurement

"An earthquake is a sudden motion or trembling of the ground produced by the abrupt displacement of rock masses".

Most earthquakes result from the movement of one rock mass past another in response to tectonic forces.

The focus is the point where the earthquake's motion starts,

The epicenter is the point on the earth's surface that is directly above the focus.

Earthquake Magnitude is a measure of the strength of an earthquake as calculated from records of the event made on a calibrated seismograph.

In 1935, Charles Richter first defined local magnitude, and the Richter scale is commonly used today to describe an

earthquake's magnitude.

Earthquake Intensity.

In contrast, earthquake intensity is a measure of the effects of an earthquake at a particular place. It is determined from observations of the earthquake's effects on people, structures and the earth's surface.

Among the many existing scales, the Modified Mercalli Intensity Scale of 12 degrees, symbolized as MM, is frequently used 

Earthquake Hazards

Earthquake hazards can be categorized as either direct hazards or indirect hazards.

Direct Hazards

¨     · Ground shaking;

¨     · Differential ground settlement;

¨     · Soil liquefaction;

¨     · Immediate landslides or mud slides, ground lurching

       and avalanches;

¨     · Permanent ground displacement along faults;

¨     · Floods from tidal waves, Sea Surges & Tsunamis

Indirect Hazards

¨     · Dam failures;

¨     · Pollution from damage to industrial plants;

¨     · Delayed landslides.

Most of the damage due to earthquakes is the result of strong ground shaking. For large magnitude events, trembling has been

felt over more than 5 million sq. km. 

Site Risks

Some common site risks are:

(I) Slope Risks - Slope instability, triggered by strong shaking may cause landslides. Rocks or boulders can roll considerable distances.

(ii) Natural Dams - Landslides in irregular topographic areas may create natural dams which may collapse when they are filled.

This can lead to potentially catastrophic avalanches after strong seismic shaking.

(iii) Volcanic Activity - Earthquakes may be associated with potential volcanic activity and may occasionally be considered as precursory phenomena.

Explosive eruptions are normally followed by ash falls and/or pyroclastic flows, volcanic lava or mud flows, and volcanic gases.

CYCLONE.

The term "cyclone" refers to all classes of storms with low atmospheric pressure at the centre, are formed when an organized system of revolving winds, clockwise in the Southern Hemisphere, anti-clockwise in the Northern Hemisphere, develops over tropical waters.

Cyclones are classified on the basis of the average speed of the wind near the centre of the system as follows:

 Wind Speed                            Classification

¨     Up to 61 km/hr                    Tropical Depression

¨     61 km/hr - 115 km/hr          Tropical Storm

¨     Greater than 115 km/hr       Hurricane

 

Hurricane.

A hurricane is a low pressure, large scale weather system which derives its energy from the latent heat of condensation of water vapor over warm tropical seas. A mature hurricane may have a diameter ranging from 150 to 1000 km with sustained wind speeds often exceeding 180 km/hr near the centre with still higher gusts.

A unique feature of a hurricane is the Eye. The eye provides a convenient frame of reference for the system, and can be tracked with radar, aircraft or satellite.

Classification

The Saffir/Simpson scale is often used to categorize hurricanes based on their wind speed and damage potential. Five categories of hurricanes are recognized:

¨     Minimal, Moderate, Extensive, Extreme & Catastrophic

The destructive potential of a hurricane is significant due to the high wind speeds, accompanying torrential rains which produce

flooding, and storm surges along the coastline

TSUNAMIS

Tsunamis are Ocean Waves produced by Earth Quakes or Underwater land slides.

The word is Japanese and means “Harbor Waves”

Tsunami is actually a series of waves that can travel at speeds from 400-600 mph in the open ocean. As the waves approach the coast, their speed decreases, but their amplitude increases.

Unusual wave heights of 10-20 ft high can be very destructive and cause many deaths and injuries.

Most deaths caused by Tsunamis are because of Drowning.

Associated risks include

·       Flooding

·       Contamination of Drinking Water

·       Fires from ruptured gas lines and tanks

·       Loss of vital Community Infrastructure [police, fire, medical]

·       Areas of greatest risks are

-Less than 25 feet above sea level

-Within 1 mile of the shore line.

Environmental Conditions left by the Tsunamis may contribute to the transmission of the following diseases

From Food or Water

·       Diarrhea illnesses;  Cholera, Acute Diarrhea, Dysentery

·       Hepatitis-A, Hepatitis-E

·       Typhoid Fever

·       Food borne illnesses;Bacterial;Viral;Parasitic;Non-infections;

From Animals or Mosquitoes

        Leptospirosis, Plague, Malaria, J.E, Dengue, Rabies

Respiratory Diseases;    Avian flu, Influenza, Measles

EFFECTS OF NUCLEAR HOLOCAUST

The effects of nuclear holocaust will result into blasts,

heat storms, secondary fires, fire, ionizing radiation and fall outs.

These effects fall into 3 categories;

1). Immediate, 2). Short term and 3). Long term effects.

¨     The immediate effects include blast effects, heat effects, electromagnetic pulse (EMP) effects and radiation effects.

¨     The short term effects include problems connected with water supply, sanitation, food, dispersal of excreta, wastes and dead bodies, break down of vector control measures and outbreak of infections. Radioactive contamination of water and food are major concerns. The affected area creates a lot of other problems for the survivors and the rescue teams.

Major problem among survivors is of bone marrow depression resulting in leucopenia, which increases their susceptibility to infections.

 

¨     Long term effects; the knowledge about the long-term effects is still incomplete. Some well known effects include radiation injuries due to radiation fallout, suppression of body immunity, chronic infection and other associated illnesses.

Persistent radiation hazards will lead to prolonged contamination of water supply, increased ultraviolet radiation, climatic and ecological disturbances, psychological disturbances and genetic abnormalities.

Current World Concern

In the light of the above facts the current world concern about the use of nuclear weapons is justified.

The world already possess an estimated total of 30,000 megatons of nuclear weapons with a total explosive power 50-100 times greater than that of all the explosives used during the Second World War.

Even if 1% of the nuclear weapons now possessed are used on urban populations, they can cause more deaths in a few hours than during the entire period of the Second World War.

The fundamental aspects of Disaster Management Program

¨     Disaster Prevention

¨     Disaster preparedness

¨     Disaster response

¨     Disaster mitigation

¨     Rehabilitation

¨     Reconstruction

 3 Fundamental Aspects of Disaster Management

 

1.    Disaster response

 

2.    Disaster Preparedness

 

3.    Disaster Mitigation   

These 3 aspects of Disaster Management corresponds to the

2 phases in the Disaster Cycle, ie,

1, Risk Reduction Phase, before a Disaster

 

2. Recovery Phase, after a Disaster   

 DISASTER RESPONSE

 OBJECTIVES

¨     Appropriate application of current technology can prevent much of the death, injury, and economic disruption resulting from disasters

¨     Morbidity and mortality resulting from disasters differ according to the type and location of the event.

¨     In any disaster, prevention should be directed towards reducing

(1) Losses due to the disaster event itself

(2) Losses resulting from the Mismanagement of disaster relief.

Therefore, the public health objectives of disaster management can be stated as follows:

1.    Prevent unnecessary morbidity, mortality, and economic loss resulting directly from the disaster.

2.    Eliminate morbidity, mortality, and economic loss directly attributable to Mismanagement of disaster relief efforts.

Nature and Extent of the Problem

Morbidity and mortality, which result from a disaster situation, can be classified into four types:

1.    Injuries, 

2.    Emotional stress,

3.    Epidemics of diseases,

4.    Increase in indigenous diseases.

The relative numbers of deaths and injuries differ on the type of disaster.

Injuries usually exceed deaths in explosions, typhoons, hurricanes, fires, famines, tornadoes, and epidemics.

Deaths frequently exceed injuries in landslides, avalanches, volcanic eruptions, tidal waves, floods, and earthquakes.

Disaster victims often exhibit emotional stress or the "disaster shock" syndrome. The syndrome consists of successive stages of shock, suggestibility, euphoria and frustration.

Each of these stages may vary in extent and duration depending on other factors. 

Epidemics are included in the definition of disaster; however, they can also be the result of other disaster situations.

Diseases, which may be associated with disasters, include

¨     specific food and/or water bone illnesses

     (e.g., typhoid, gastroenteritis and cholera),

¨     vector bone illnesses

    (e.g., plague and malaria),

¨     diseases spread by person-to-person contact

     (e.g., hepatitis A and shigellosis)

¨     Diseases spread by the respiratory route

     (e.g., measles and influenza).

·       The current status of environmental sanitation, disease surveillance, and preventive medicine has led to a significant reduction in the threat of epidemics following disaster.

 

·       Immunization programs are rarely indicated as a specific post disaster measure. 

·       A disaster is often followed by an increase in the prevalence of diseases indigenous to the area due to the disruption of medical and other health facilities and programs.

Morbidity and Mortality from Mismanagement of Relief

Ideally, attempts to mitigate the results of a disaster would not add to the negative consequences;

However, there have been many instances in which inappropriate and/or incomplete management actions taken after a disaster contributed to unnecessary morbidity, mortality, and a waste of resources.

Many of the Causalities and much more of the Destruction occurring to natural disaster are due to ignorance and neglect on the part of the individuals and public authorities.

There is a plethora of literature describing the inappropriate actions taken to manage past disasters. Many of the same mismanagement problems tend to recur.

¨     Physicians and nurses have been sent into disaster areas in numbers far in excess of actual need.

¨     Medical and paramedical personnel have often been hampered by the lack of the specific supplies they need to apply their skills to the disaster situation.

¨     In some disasters, available supplies have not been inventoried until well after the disaster, resulting in the importation of material which is used or needed.

In a study of past disaster mismanagement problems and their causes, these problems were categorized as follows:

1.    Inadequate appraisal of damages

2.    Inadequate problem ranking

3.    Inadequate identification of resources

4.    Inadequate location of resources

5.    Inadequate transportation of resources

6.    Inadequate utilization of resources