Causes of emergency situation origin, stages of their development and hit site

The emergency situation appears as result of:

- rapid natural processes caused by gravity, earth circulation or temperature difference;

- effect of the external natural factors, which result in aging or corrosion of materials of constructions, structures and decreasing of physical-mechanical parameters;

- engineering-industrial defects of structures (designer's error; low quality of materials; breaking the rules of safety precautions for repairing and other works);

- influence of technological processes on materials of structures (overloading; high temperatures, vibration, aggressive medium);

- breaking of safety regulations of construction and technological processes, which induce kettle explosion, chemical substances spreading etc;

-military activity of all kinds.

Irrespective to the origin and type emergency situation development has four inherent stages (phases): origin, initiation, culmination and fading (liquidation of consequences).

At the origin stage the conditions, premise for future ES get formed: unfavorable natural processes are activated; the engineering-industrial defects of structures are accumulated, multiple technical breakdowns appear; equipment malfunctions.

To define duration of origin stage is possible approximately only by means of regular statistics of failures, breakdowns, «local» failures, observations of seismic, meteorological, mudflow struggling and other stations.

At the initiation stage of ES the most essential influence belongs to the human factor. Statistics testifies that more than 60% of accidents arise because of staff errors.

At the culmination stage releasing of energy or substance which makes unfavorable effect on people and environment occurs, at that moment the extreme situation appears. The characteristic emergency event is chain character of passing, when destructive action of the initiating event gets many times increased owing to engaging into the process powerful, toxic or biologically active components. It is the chain process of destroying energy and substances releasing.

The fading stage covers time from interception of the source of danger - localization of ES, to complete liquidation of its consequences, including all the chain of secondary, tertian and other consequences. The duration of this stage can make a year, and sometime a decade.

The knowledge of ES development chain in concrete conditions enables to reduce the risk for such situation originating to ensure readiness for emergency circumstances.

The territory on which the dangerous and harmful factors of ES act, with people, animals, structures, and communications located in is called as hit site. It is simple and complicated.

Simple hit site occurs under influence of one hit factor, for example, ruining from explosion, fire, only chemical or bacteriological contamination.

Complicated hit site arises owing to the force of several hit factors of ES. For example, the explosion at the chemical plant entails ruin, fire, chemical contamination of surroundings; earthquake and hurricane ruining structures can induce floods, fire from damage of an electrical network etc.

The shape of hit sites depends on a nature of a source of the dangerous factors and can be round on earthquake, explosion; band on hurricane, flood, mudflow; irregular on fire, tsunami and other.

Consequences can be various; they depend on type, character and scale of ES distribution.

Main consequences of ES are: death, disease of the people, ruin, radioactive polluting, chemical and bacteriological contamination. People who turned out to be in extreme conditions of ES get under affect of psycho-traumatic circumstance which induces violation of mental activity, the so called reactive condition. The reactive action of extreme conditions is made not only by direct danger for the life of the person, but also is connected with expectation of its realization outside the hit site.

If the radiuses of dangerous and harmful factors action can be defined beforehand by calculation methods, on contrary the radius of psychological action actually can vary. In some cases it can be many times larger than other hit factors radiuses.

4.3 Classification and general characteristicsof emergency situations

Each ES has the physical essence, origin causes, destroying forces, development character, features of action on human and surroundings. Therefore classification structure of ES is based on character of their genesis (cause of origin), velocity of development (velocity of danger distribution), scale of distribution of the hit factors with the regard for consequences, and also on the victim’s quantity.

According to the cause of origin ES are divided into: natural disaster, man-caused catastrophe, anthropogenous and ecological catastrophes, social - political conflicts.

Natural disaster is a dangerous natural phenomenon or process, which has an extreme character and result in disturbing of daily life of the people, and also erasure of material resources. It includes earthquake, flood, tsunami, hurricane, wood and peat fires and other. The drought, strong frost, long rain, epidemic, spreading of wreckers of wood and agriculture refer to natural disaster too.

Classification of natural disaster.

There're 3 groups of natural catastrophes:

- tectonic catastrophe (earthquake, eruption of volcano);

- topological catastrophe (flood, snow avalanche);

- meteorological catastrophe (hurricane, typhoon, frost and other).

Natural disasters cause national economy going down, eliminating of material resources, and what's the most, essential, people victims, destroying their living place and property. Besides, they can become a reason for mass infection diseases. Most, people suffer from floods (40%), hurricanes (20%), earthquakes and droughts (15%). Near 10 % are the rest of natural disasters types.

Here the characteristic for some natural catastrophes is given.

The earthquake is the force shacking of the earth's crust induced by tectonic or volcanic cause that results in ruin of structures, fires and people victims.

Main earthquake characteristics are size of hit site, magnitude, intensity of energy on the earth surface. Earthquake's size of hit site can be of 10-30 km, sometimes it is much more.

Magnitude characterizes general energy of earthquake and represents a common logarithm of ratio of maximum ground oscillation amplitude measured in the investigated place by seismograph in microns to maximum amplitude of ground oscillation defined on the distance of 100 km from the epicenter.

Magnitude (M) by Richter scale is measured from 0 up to 9 (last number corresponds to the most powerful earthquake),

The intensity of energy on the surface of the ground is measured in numbers. It depends on hit site size, magnitude, distance from epicenter, and geological structure of the ground. For earthquake energy intensity measurement in our country 12-numbers Richter scale is accepted.

Earthquake characteristic:

`The earthquakes bring large material losses and kill thousands people.

For example, on June 21, 1990 during earthquake having intensity of 8 numbers by the Richter scale at Northern Iran in the province of Shlyan more than 50000 people perished and about 1,000,000 people were injured and left out of living places.

The largest earthquakes of XX century.

Protection from earthquakes implies beforehand detecting of seismic dangerous zones in various regions of country, which is seismic zoning. On maps of seismic zones where earthquakes of intensity above 7-8 numbers by Richter scale are possible are marked. In such regions they carry out various protective measures, chemical factories and nuclear power stations are not admitted to build in.

Flood is significant water filling of district after increasing of water level in river, lake caused by various reasons (rain, ice jam on the rivers, dam destruction and other). Floods result in material losses and human victims.

At the beginning of July, 1990 heavy showers in Zabaykallia caused the flood which destroyed 400 bridges and brought the losses of 400,000,000 in national currency. Thousands people remained without living place or perished.

Floods can cause fires as the result of short-circuit of power cable, and also destruction of pipes, electrical, television and telegraphic networks.

The main direction in flood struggle is decreasing of maximum water gain in a river by the redistribution of the flow in time (preservation of plants near water, planting of forest shelter belts etc). For the protection from flood the system of dams is used.

Land-slide is shifting of mountain masses down the slope, which appears because of equilibrium breaking caused by many reasons (ground undermining, unreasonable economic activity etc).

Land-slides can take place in all hills with slope 200 and more in any season. They differ both in speed of mass moving (slow, middle and fast), and in scale. The slow slides speed makes tens centimeters per one year, middle - some meters per hour or 24 hours, fast - tens kilometers per hour and even more. Only fast slides can get the cause of catastrophes with people victims. For example, in 1911 in the Pamirs the powerful earthquake (M = 7,4) induced large land-slide. Near 2,500,000,000 m³ of loose masses moved down. Village Usoi with 54 residents was dumped. The land-slide has parted off the valley of the river Murgay and created the dump lake which has flooded the village of Saraz. The height of that natural dam reached 300 m, depth of the lake - 284 m and length - 53 km.

Precaution measures are transformation of ground relief, fixing of a slope by piles, construction of supports.

Snow avalanches are also referred to land-slides and appear as sliding displacements. Gravity makes displacement of snow masses down the slope. Show avalanche is a compound of snow crystals and air. Large avalanches arise on 25-600 slopes. For example, on July 13, 1990 in the Pamirs the earthquake and snow avalanche demolished camp of the climbers, which was located on the height of 5300 m, 40 men perished.

The protection from avalanches can be passive and active. In passive protection protecting shields are applied. In active protection avalanche-dangerous slopes shooting is carried out.

Mudflow is a flood with a very large concentration of mineral particles, stones, fragments of mountain rock (what makes from 10-15 up to 75% of total flow volume), which occurs in pools of small mountain rivers and is caused by rain, sometimes by intensive snow thawing. Danger of mudflow consists not only in its destroying force, but also in suddenness of its origin. Mudflow can be of mud structure (mixture of water and soil), mud-stone structure (mixture of water, rubble, gravel, and small stone), water-stone structure (mixture of water and large stone). The mudflow speed reaches 2,5-4,0 m/s, and sometimes up to 8-10 m/s. Mudflow consequences are sometimes disastrous. On July 8, 1921 Alma-Ata was hit by the mass of the ground, stone, snow, sand accelerated by the water flow. That flow demolished structures, people, and animals. The buildings were taken off the foundation and together with people taken by a rough flow.

One mudflow was caused by the showers in the pool of the river Mala Almaatinka. The total volume of mud-stone masses made near 2,000,000 m³. The flow intersected city by 200-meter band.

Methods for mudflow struggling are various. These are structure of various dams, cascade of jams, supports, ditch etc.

Hurricane is a wind having force of 12 numbers by the Bofft scale, that is the wind blowing over 32,6 m/s (117,3 km/h). Hurricanes are also tropical cyclones which arise in the Pacific Ocean near Central America; on the Far East and the Indian Ocean hurricanes are named as typhoons. In hurricanes the velocity of the air reaches more than 50 m/s. They are followed by heavy showers.

In December, 1944 near the Philippines the ships of the 3^rd USA Navy turned out to be near the center of the typhoon. Three destroyers drowned, other 28 ships received damages, 146 planes and 19 hydroplanes were broken and got out of the board, more than 800 people perished.

Hurricanes and storm wind (20,8 up to 32,6 m/s by the Bofft scale) in winter can rise plenty of snow in the air making a snowstorm. From hurricane wind and large waves in East Pakistan about 10,000,000 people suffered and approximately 500,000 perished on November 13, 1970.

Modern methods of the weather forecast allow a couple of hours or even a day before to warn people about hurricane coming up. The most reliable protection from hurricanes is using of protective structures (subway, cellars of houses, underground transitions etc can be applied as).

Man-caused catastrophe is a sudden breakdown of machines, mechanisms and aggregates during their operation, what's followed by serious failure of technological process, explosion, and fire, radioactive, chemical and biological polluting of large territories, people victims.

Failures at the industrial objects, construction, and also on railway, air, auto-transport, pipeline which cause fire, destroying of civil and industrial structures, danger of radiation, chemical and bacteriological polluting of surroundings and also other consequences represent danger for people and environment.

The character of man-caused catastrophe consequences depends on the type of an accident, its scales and features of the place where it occurred.

Man-caused catastrophe can be consequences of the external natural factors action, including natural disasters, engineering-industrial structures, breaking of technological processes, breaking of safety regulations for transport and machines operation etc. But most often reason is breaking of technological process and occupational safety.

Anthropogenous catastrophes are qualitative change of the biosphere caused by an action of the anthropogenous factors which have taken place during people economic activity and harmfully influence on people, animals and plants, surroundings.

Degradation of the environment is a consequence of urbanization, extension of economic activity, wrong treatment to nature.

Emergency situations of ecological character include intensive degradation of the ground and its polluting with heavy metals (cadmium, mercury, lead, chromium), contamination of atmosphere by harmful chemical substances, noise, electromagnetic fields and ionizing radiation, contamination by acid rains, elimination of ozone layer; smog, contamination of water.

Social-political conflicts are very critical form of solution of the disagreement between the countries using modern methods for attack (military-political conflicts), and also international crisis followed by violence. '

According to velocity of danger distribution ES are classified as sudden (earthquakes, explosions, transport accidents), fast (fire, hydro-dynamic breakdowns with forming of break wave), moderate (floods, accidents followed with radioactive substances ejection), smooth - with slow distribution of danger (drought, epidemics, ground and water contamination by harmful chemical substances).

According to complex indications ES are divided into 5 types: place, local, regional, national and global. Place ES consequence spreads in the boundaries of an object of national economy and can be liquidated by its own forces and resources.

Local ES scales in the boundaries of the locality and can be liquidated by forces and resources of district.

Regional ES consequences cover space in the boundaries of a number of districts or economic region and can be liquidated by forces and resources of country.

National ES have consequences covering several economic regions, but don't exceed boundaries of country. The liquidation of such ES is carried out by forces and resources of the country, frequently with the help of other countries.

Global ES consequences get over boundaries of the country and spread over the other countries. These consequences are liquidated as by forces of each country on the territory so by forces of international union.

According to amount of victims ES can be small (25-100 people hurt, 10-15 people hospitalized), middle (100-1000 people hurt, 50-200 people hospitalized), large (it is more 1000 people hurt, more 200 people hospitalized).