C HAPTER III
H AZARD , R ISK
AND
V ULNERABILITY A NALYSIS
District New Delhi being a part of
combination, can not be studied in isolation for
hazard profile for the district. The type of risks
same as that of the whole of Delhi. The hazards
and man-made.
Delhi, a unique city-state
the purpose of developing a
New Delhi is prone to is the
can be classified into natural
Delhi is prone to natural hazards like Earthquake and floods while
manmade hazards like fire and terrorism etc. there for this chapter discuses
the issues, and risks involved fro difference hazards Delhi is prone to.
Figure 1: Delhi Hazards
District Disaster Management Plan, New Delhi
18
Earthquake
An earthquake is a sudden motion or trembling of the ground produced
by abrupt displacement of rock masses, usually within the upper 15 to 50 km
of the Earth’s crust. Most earthquakes result from the movement of one rock
mass past another in response to tectonic forces. Rock is elastic and can, up
to a point, accumulate strain where adjacent areas of rock are subjected to
forces pushing or pulling them. When the stress exceeds the strength of the
rock, the rock breaks along a pre-existing or new fracture plane called a fault
(Figure 1.1).
The rupture extends outwards along the fault plane from its point of
origin, or focus. The epicentre of an earthquake is the point on the Earth’s
surface that is directly above the focus. The rupture usually dos not proceed
uniformly; its progress typically is jerky and irregular. Variations in rock
properties and overburden pressures can bring the rupture almost to a stop;
then because of there arrangement of elastic forces, the rupture suddenly
may break free and swiftly move out. The rupture will continue until it
reaches the places at which the rock is not sufficiently stained to permit it to
propagate further. If the rupture reaches the surface, it produces a visible
surface break (Figure 1.2).
During the rupture, the sides of the fault rub against one another so
that considerable energy is expended by frictional forces and in the crushing
of rock. The surfaces are heated locally. Earthquake waves are generated at
the same time by the rebounding of the adjacent sides of the fault at the
rupture surfaces, as well as by rubbing and crushing. The seismic energy is
emitted from the rupture as seismic waves. The fastest are the primary (or
P).
Waves, also called compressional waves, which are compressiondilation waves and travel in average crystal rocks at about 5km per second.
The secondary (or S) waves, which are slower, are shear waves with a speed
in the crust of about 3km per second. The slowest waves are surface waves,
called Rayleigh and Love waves, whose depths of penetration are dependent
on their wavelengths. They travel near the surface of the surface of the Earth
with a speed of less than 3km per second.
Earthquakes are considered to be one of the most dangerous and
destructive natural hazards. The impact of this phenomenon is sudden with
very little or without any warning. It is not yet possible to make a prediction
about earthquake’s occurrence and magnitude. A very large number of
earthquakes occur every year all round the earth but only a limited number f
them are centred near populated areas or are having sufficient strength to
cause damage to built environment.
District Disaster Management Plan, New Delhi
19
Earthquake Scales: Magnitude and Intensity
Earthquakes are described in terms of their magnitude (M) and
intensity (I). These are two distinct scales which should not be confused.
Earthquake magnitude is a measure of strength of an earthquake, i.e., the
strain energy released at its source. Earthquake intensity is a measure of the
observed effects of the earthquake on man, buildings and the earth’s surface
at a particular place.
Magnitude, as the logarithm, to the base 10, of the amplitude in
micrometers of the maximum amplitude of seismic waves that would be
observed on a standard torsion seismograph at a distance of about periods
100km from the epicentre. The seismic waves used for local magnitude have
periods ranging approximately from 0.1 to 2 seconds, equivalent to a
wavelength of 300 meters to 6km.
Since 1935, more than half a dozen different magnitude scales have
been devised to measure earthquake magnitude. Most magnitudes of
earthquake occurring at great distances (more than about 600km) from a
seismograph station are determined using the logarithm of the amplitude of
the surface or body waves with a period of 20 second (a wavelength of about
60km), which are often dominant on the seismograms. The bodywave
magnitude scale (Mb) measure seismic bodywaves, primary (P) and
secondary (S) which have period usually from 1 to 10 seconds.
Although the magnitude scale is logarithmic, the energy associated
with an increase of one degree of magnitude is not ten-fold, but about thirtyfold. For example, approximately 900 times more energy is released in a
magnitude 7 earthquake than in a magnitude 5earthquake. The 1964 Alaskan
earthquake, for example, of magnitude (M) 9.2 released 45*1025
(450,000,000,000,000,000,000,000,000) ergs of seismic energy, i.e., the
equivalent of the total energy consumption for the USA in the year. The
Alaskan earthquake is one of the largest instrumental (as opposed to
historical) earthquakes ever recorded. The public systematically confuses the
two scales, referring to the Richter 9-point, and even 12-point, scale! It must
be understood that the Richter magnitude (M) scale is open-ended. It must
also be understood that earthquake magnitude is not, strictly-speaking, an
adequate planning or mitigation tool, unless magnitude/intensity relationship
can be established for a particular area or region. The intensity scale is the
most commonly used for building and planning.
Intensity
Earthquake intensity is a measure of the effects of an earthquake at a
particular place. Intensity is determined from observation of an earthquake’s
effect on people, structures, and the Earth’ surface. This first intensity scale
to gain wide use was developed in Europe in 1883 by M.S. DeRossi of Italy
and F.G. Forel of Switzerland. The Rossi-Forel scale grouped earthquake
effects into 10 steps of intensity beginning with 1 for the least noticeable.
The Rossi-Forel scale proved too peculiar to 19 th century Europe to be
District Disaster Management Plan, New Delhi
20
universally applicable. In 1902, Giuseppe Mercalli, improved scale which also
had 10 grades of intensity (later increased 0 12).
Two intensity scales are used today: the Modified Mercalli scale (short
version of 1931) symbolized as MM; and the Medvedev-Sponheer-Karmic
scale of 1964, known as the MSK scale. The MM scale is used in the certain
western countries of Europe. The MSK scale is used predominantly in Eastern
Europe. The MSK scale is a much more elaborate and explicit scale than the
MM scale but both are useful and valid.
Hazards and Impacts associated with an earthquake:
Earthquake cause a variety of impacts on the crust of earth. Various hazards
associated with an earthquake can be grouped as following:
•
Primary Hazards: These are the effects, which occur simultaneously
alongwith natural phenomenon of the earthquake:
•
Ground shaking
•
Fault rupture
•
Tectonic deformations
•
Secondary Hazards: These effects are those, which occur at the end or
after the earthquake phenomenon:
•
Soil liquefaction
•
Land and Mud slides
Due to these hazards associated with an earthquake, a number of
impacts occur. The impacts of an earthquake may also be grouped in the
same manner on the basis of the type of hazard, as mentioned below:Primary Impacts:
•
Building and Bridge collapse
•
Rupture of water and gas pipelines and other utilities
•
Changes in underground water sources
•
Changes in courses of rivers
•
Secondary Impacts:
•
Death and damage due to collapse of infrastructure including buildings
•
Fire and explosions
•
Disease and epidemics
•
Floods
•
Assessment and Mapping
District Disaster Management Plan, New Delhi
21
Seismic Zoning
Seismic zoning consists of dividing a national territory into several
areas indicating progressive levels of expected seismic intensity for different
return periods. These zones can be described in terms of expected intensity,
peak ground accelerations, or any other strong ground-motion parameter.
The number of zones into which a country is divided is fairly arbitrary. Zoning
at the territorial or national levels depends on the collection and analysis of
historical and instrumental records of strong ground-motion. For example, a
country may be divided into three, four or more seismic zones. The definition
of these is a matter not only of technical but also of administrative
competence.
Seismic Micro-Zoning
Hazard micro-zoning consists of recording in detail all seismological,
geological and hydro-geological parameters that may be needed in planning
and implementing a given project area at an appropriate scale for physical
planners, urban designers, engineers and architects, or any other user.
Seismic micro-zoning consists in mapping in detail all possible
earthquake and earthquake-induced hazards. These maps should contain
information that is limited to the users` requirements, and presented in a
from comprehensible to them. Invariably, the users` maps will be different to
those prepared by or for the specialists. This is a problem which has yet to
be properly explored.
Type of Studies Required
The physical framework of a study zone and the localizing of urban
sites chosen by national or local authorities for the detailed study of seismic
micro-zoning must be selected beforehand. The main aim of seismic microzoning is the definition of seismic hazards which may affect the areas in
question and to present data in summary form so that it may be useful to
governmental agencies, urban planners and the building industry.
The results will be used to facilitate either the planning or the repair
and strengthening of buildings destroyed or damaged by previous
earthquake. These results will contribute to urban planning and the design of
new buildings in the selected urban areas. This in turn will limit the
potentially destructive effects of future earthquakes.
The framework for any micro-zoning study must include the following
tasks:
A geological survey of the sites concerned in order to identify those which are
potentially dangerous, such as those which follow active faults or which are
susceptible to landslides, and to delimit spatially surface deposits.
District Disaster Management Plan, New Delhi
22
A compilation and analysis if existing geotechnical data in addition to that
already provided by drilling and trial wells undertaken during rests, including
the results of laboratory tests. These tests characterize the geotechnical
properties of the lithological unit identified on photo geological maps of urban
areas and show and three dimensional variation information.
A compilation of available hydrogeological data which allows the calculation
of the liquefaction potential of urban areas soils.
Determination of maximum ground acceleration for return periods of 50,200
and 500 years, and the development of typical spectra for the different
general categories of subsurface conditions which take into account all the
sites under study.
An evaluation of flood potential in urban zones due to tectonic collapse or
upheaval of river beds, or due to landslips, caused by an earthquake which
could block ricer flow.
The preparation of summary maps of seismic hazards and of micro-zoning for
each of the urban zones. These maps should contain potential seismic
hazards and dived each district into zones of comparable risk due to the
combined effects of these hazards.
The result must be annotated and specific to each site. Data contained
in the analysis of seismic hazard for a given zone must also be useful for
evaluating potential secondary effects such as the breakdown of transport
infrastructure (roads, railways, pipelines, aqueducts or electric power lines),
or flooding caused by dam failure due to earthquake.
Movement – Earthquakes
Earthquakes are caused by sudden movements along a geological fault
in rock comparatively near to the earth’s surface. Most movement are
preceded by the slow build-up of tectonic strain which progressively deforms
the crystal rocks and produces stored elastic energy. When the impressed
stresses exceed the strength of the rock it fractures, usually along a line of
pre-existing weakness known as a fault. This sudden rupture releases the
stored strain energy and produces seismic waves which radiate outwards
ever-widening circles. It is the fracture of the stressed rocks, followed by
elastic rebounding on either side of the fracture to a less strained position,
which is the cause of ground-shaking. The displacement of rocks mat be
either vertical or horizontal and is often visible at the ground surface in the
form of small fault scarps or the lateral offsetting of streams or roads
respectively.
The point of rupture, known as the focus, can occur anywhere between
the earth’s surface and a depth of 600-700 km. Shallow-focus earthquakes
(km. below the surface) are the most damaging events, accounting for about
three-quarters of the global seismic energy release. For example, the San
District Disaster Management Plan, New Delhi
23
Fernando, California, earthquake of 1971 had only a moderate magnitude
(M=6.4 on the Richter scale) but, because it occurred only 13 km. below the
surface, much damage was created. The source point for earthquake
measurement is the epicentre, which lies on the earth’s surface directly
above the focus.
The main environment al hazard created by seismic earth movements
is ground-shaking. This term, which is used to describe the vibration of
ground during an earthquake, can be explained in the basis of three types of
elastic wave—primary, secondary or surface. The primary, or P wave, is a
Compressional or longitudinal wave, similar to a shunt through a line of
connected rail coaches. It spreads out from the focus, with seismic vibration
following the direction in which the wave travels at a fast speed of about 8km
s-1, depending on the density and elastic properties of the rock through
which it travels. These P waves, like sound waves, are able to travel through
both solid rock and liquids, such as the oceans. The secondary S waves move
at about half the speed of primary waves and cause vibration at right angles
to the direction of wave travel. S waves cannot propagate in the liquid parts
of the earth but, when they reach the surface, the resulting vertical ground
motion is highly damaging to structures. However, most structural damage
beyond a few kilometres from the epicentre is associated with the surface
waves, which are either Love waves or Rayleigh waves. Love waves pose a
special problem for the foundations of buildings. They do not possess vertical
motion but shake the ground horizontally at right angles to the direction of
propagate. Love waves usually travel faster than the Rayleigh waves which
operate a little like ocean wave with fairly high amplitude of vertical motion.
The severity of ground-shaking at any point depends on a complex
combination of the magnitude of the earthquake, the distance from the
rupture and the local geological conditions, which may either amplify or
reduce the earthquake waves. This shaking, expressed in terms of both speed
and amount of ground motion, is measured by accelerographs. Put simply,
ground acceleration refers to the rate at which the earth is moved, both
horizontally and vertically, by the force of the earthquake. Acceleration is
usually expressed in units of 1.0g, or the acceleration due to gravity (9.8 ms2). An acceleration greater than 1.0g in the vertical plane means tat
unsecured objects would leave the ground. For some time it was thought that
a maximum possible peak acceleration in firm ground might be around 0.5g
but values as large as 0.8g have been recorded from earthquake with Richter
magnitudes as small as 3.5. It now seems possible that peak accelerations
may exceed 2.0g (EERI, 1986).It should also be noted that peak acceleration
decreases quite rapidly within 50 km. of the earthquake source, although the
detailed pattern will depend on local geology and soil conditions.
The greatest structural damage is created by horizontal ground
movements. This is partly because all buildings are constructed to resist the
pull of gravity and can, therefore, withstand some vertical movement.
However, weak structures may be unable to cope with horizontal
accelerations as little as 0.1g.The significance of horizontal ground-shaking is
further increased by the fact that peak horizontal accelerations are commonly
double those in the vertical plane. The vertical component of shaking in a
District Disaster Management Plan, New Delhi
24
California earthquake reached a peak slightly above 0.1g in response to the
arrival of the P waves. However, on the east-west axis of shaking, peak
horizontal ground-shaking reached just over 0.2g between 3 and 4 seconds
after the record began following the arrival of the S waves. The north-south
shaking shows a similar pattern.
Most strong-motion measurements depict ground-shaking as a function
of time. This is because the scale of destruction also depends in the
frequency of the vibrations. The frequency of a wave is the number of
vibrations (cycles) per second measured in units called Hertz (Hz) High
frequency waves tend to have high accelerations but relatively small
amplitudes of displacement. Low frequency waves have small accelerations
but large velocities and displacements. During earthquakes, the ground may
vibrate at all frequencies vibrations (D1 Hz) which are most effective in
shaking low buildings. Rayleigh and Love waves are lower frequency and are
usually more effective in causing tall buildings to vibrate. The very lowest
frequency waves may have less than one cycle per hour and have
wavelengths of 1,000 km or more.
The effect of wave frequency can be demonstrated in the 1985 Mexico
City earthquake some of the taller building survived because their natural
resonant frequency did not match the high frequency shock waves. However
many of the shorter buildings collapsed. On the other hand, in the 1964
Alaska earthquake, a lot of low frequency vibrations were produced. These
would normally have toppled high structures but, since most buildings
affected in Alaska were low rise many of them survived. The strong groundshaking in the Loma Prieta earthquake, which hit northern California in 1989,
lasted for only 6-10 seconds. This was sufficient to throw down some
structures built on estuarine mud and alluvium, which amplified the ground
movement. But the duration of shaking was not enough to causes widespread
liquefaction of soils in the Bay Area which would have caused the failure of
many more building. Local site conditions have important effe4cts on strong
ground motion. For example, significant amplifications occur in the steep
topography, especially on ridge crests. Ground motion in soil are enhanced in
both amplitude and duration, compare to those recorded in rock. This agrees
with the general observation that structural damage is usually more severe
for buildings founded on unconsolidated material rather than rock. For
example, in the Maxico City earthquake of 1985 the recorded peak ground
accelerations varied by a factor of 5. Strong-motion records obtained on firm
soil showed values of around 0.04g. This compared with observations from
the central part of Maxico City, which is founded on a dried lake bed, where
the measured peak ground accelerations reached 0.2g.Similar effects were
noted in the San Salvador earthquake of 1986. This had a modest size
(M=5.4) but produced large-scale impacts, including the destruction of
thousands of buildings, 1,500 deaths, 10,000 injuries and a quarter of a
million people homeless. The unusual devastation was rooted in layers of
volcanic ash, up to 25 m thick, which underlie much of the city. As the threesecond long earthquake tremor passed upwards through the ash, the
amplitude of ground movement was magnified up to five times.
District Disaster Management Plan, New Delhi
25
Adjustments
Earthquake disasters are second only to wars and civil strife in
attracting funds because of the catastrophic loss of life. This is not
necessarily desirable because the number of deaths in an event is still a ling
way to go before earthquake disaster assistance is optimized. In the first few
days after the Mexico City earthquake of 1985, the government turned down
offers of foreign aid in the belief that it could cope alone. Deposit the
subsequent massive in infusion of aid, the official rescue and relief
programme appeared to have only a minor effect. A survey of residents in
the badly damaged area showed that few had received assistance and that
even fewer had experienced contact with organizations involved in the
delivery of relief goods. Some groups set up their own rescue services to
bypass the uneven government effort.
The earthquake which struck the republic of Armenia, UAAR, in 1988
killed ay least 25,000 people, made 514,000 homeless and resulted in the
evacuation of nearly 200,000 persons. Following the Soviet government’s
decision to accept international aid, over 67 nations offered cash and
services amounting to over $200 million. Most of the earthquake damage
seismic standards were relaxed. The Soviets announced a programme to
rebuild the cities within a two-year period on sites in safer areas and with
building heights restricted to four storeys in Leninakan during the first year
were actually completed. Consequently, many people were still living as
evacuees in neighbouring republics or in temporary shelters close to their
home villages many months after the disaster.
Insurance
Earthquake insurance is available in a number of countries such as
Japan, New Zealand the Soviet Union and the United State. But the capacity
of private companies to cope with the potential losses is limited. A
catastrophic earthquake is probably the greatest natural hazard faced by the
USA with an estimated 70 million Americans exposed to severe risk and an
additional 120 million exposed to moderate risk. Breakdown of losses likely
to be suffered by the insurance industry following major (M=approx.8.0)
earthquake along the northern San Andreas and Newport-Inglewood faults in
California. There is a real possibility that the US might experience a major
earthquake within the period 1990-2010 with costs exceeding $100 billion. It
is doubtful if the private insurance
Industry has either the capacity to make available all the cover which
might be sought against this scale of disaster or has the reserves to meet the
claims that would ensue. Even the relatively modest Loma Prieta earthquake
(M= 7.1), which struck San Francisco in October 1989, created at least 62
dead, with some 13,000 homeless and damage variously estimated up to $10
billion .
The vast majority of the exposed risk from ear6thquakes is presently
uninsured, even in those countries where government-supported schemes
have been introduced. Most policies are on commercial and industrial
District Disaster Management Plan, New Delhi
26
property rather than residential property. In the San Fernando, California,
earthquake of 1971 property damage amounted to some $500 million, of
which only $32 million was covered by insurance. Since the subsequent
disaster loan programme provided over $257 million in aid, it is evident that
the general tax-payer assumes much of the financial burden. It has been
estimated that less than 5 per cent of the California property insured against
fire is also insured against earthquake, probably as a result of dissonant
perception’.
Most earthquake insurance policies are intended to cover catastrophes
rather than small losses. As a result, they usually have a deductible amount
that is either a percentage of the insured value or a fixed cash amount. For
home-owner the deduction is often 5 per cent of the insured value. This
deductible amount presents a deterrent to the purchase of insurance,
especially for the owner of a modern wood frame house which is likely to
suffer only moderate damage. After the 1971 San Fernando earthquake, the
average cost off repairs was 6.6 per cent of the insured value and some
owner argue that it is wiser to spend money on strengthening buildings
rather than in insurance premiums. In California, the cost of insurance is
rated according to location, Type of construction and soil conditions. The
state is divided into three risk zones and premium rates rise progressively
from small wood-frame houses to unreinforced masonry. A building on filled
land, for example, might well attract a 25 per cent surcharge.
Environmental Control
At the present time, there appears to be little prospect of human being
able to suppress earthquakes. Therefore, the most effective adjustment
would involve the deliberate inducement of small-scale seismicity in order to
prevent the accumulation of potentially damaging strain energy.
One
approach lies in the manipulation of surface water resources in a hazardous
fault zone. There are well-documented cases of man-made reservoirs in
induci8ng relatively small events. It is thought that the extra load of water
on the earth’s crust is sufficient to trigger shallow earthquakes along
sensitive fault- lines. The effect was first observed with the creation of Lake
Mead on the Colorado River in 1935. However, as emphasized by Bolt et
al.,(1975) in other tectonically active areas the construction of large dams
has not led to more earthquakes. The best practical use of this information
would be attempted to reduce a threatened earthquake by deliberately
lowering the water level in a reservoir. The release of stored water would
also minimise the risk of dam failure and downstream flooding.
Another possibility exists in the manipulation of groundwater levels. A
large head of groundwater, associated with a high water table, would tend to
increase the pore pressure within saturated rocks thereby reducing the
frictional resistance along a fracture. This would encourage slippage along
the fault rather than the accumulation of tectonic strain. There is already
evidence that the disposal of liquid waste into boreholes has created such an
effect and it may be that the artificial lubrication of faults by the injection of
water could help to control the build-up of hazardous tectonic strain.
District Disaster Management Plan, New Delhi
27
Vulnerability Modification Adjustments
Avoidance of high-risk earthquake areas is the most direct land use
adjustment. The microzonation of land with the aim of converting already
developed area to parkland or similar uses, and the prevention of further
development at hazardous sites, must be a priority. Such a policy depends on
the public availability of information and there are problems not only in
making the information available, but also in ensuring a satisfactory public
response.
In California state law requires that estate agents inform al home
purchasers if properties are located near to mapped fault-lines. It is likely
that newcomers to such hazard areas will be most in need of such
information and will also be most likely to heed the advice, assuming that
they have few preconceived ideas about the desirability of different
residential areas. However, palm (1981) showed that estate agents were not
effective communicators of hazard information, mainly because the hazard
potential of property was not disclosed until sale negotiations were well
advanced. In this case the price and sales of hazard-prone property have not
declined as anticipated. In the most desirable residential areas, other
attributes—such as schools, shops, investment potential, view—appear more
important to buyers than uncertain risk, especially if the purchaser intends to
relocate in a few years time.
Rezoning of low-lying coastal land at risk from tsunamis, in association
with structural strengthening of buildings, can be an effective defence. For
example, Crescent City, California, was badly damaged by a tsunami after
the 1964 Alaska earthquake. Since then the waterfront has been redeveloped
into a public park and the beach area has been rezoned with business
premises now located back from the shore on higher ground. Press (1983)
has emphasized the need for tsunami mitigation to be explicitly integrated
into the planning of hazard-prone coastlines so that evacuation routes, for
examples, can be prepared and protected. A variety of measures which could
be taken to incorporate into a comprehensive scheme to create a buffer zone
against tsunamis, including the protection of structures and the protection
structures and the provision of a coastal evacuation route.
The Vulnerability of Buildings
Within the investigation area a number of transacts were taken across
the zone of major damage in order to examine the performance of buildings
during the earthquake. Along the trans acts each and every building was
examined; types and heights of construction were noted, together with
information concerning building damage. The results of the survey are
summarised. This shows that on the lake bed, rigid structures (e.g., stone
masonry buildings) generally performed better than relatively flexible ones
(e.g., many of the reinforced concrete structures).
The greatest single influence on building vulnerability, however, was
height construction. Medium to high- rise buildings between 6 to 20 stores
were worst affected, with those between 9 and 11 experiencing the highest
District Disaster Management Plan, New Delhi
28
incidence of damage. The area of major damage on the lake bed was largely
confined to that part where the density of medium to high- rise building was
greatest. Damage was considerably restricted in Building Elevation Zone III
where 98.5% of the buildings were less than 6 stores high. Unfortunately no
data were available for the remainder of the lake bed, although
reconnaissance of the area to the east of Building Elevation Zone III revealed
that the vast majority of buildings were low- rise at the time of the time of
the earthquake.
Medium to high-rise buildings tend to have lower natural frequencies
of vibration than low-rise ones. They were therefore much more likely to be
sensitive to and “in-tune” with, the low-frequency ground motions
experienced in Mexico City during the earthquake. This had the effect of
causing many of the buildings to resonate, thereby prolonging and reinforcing
the vibration within them. This was heightened in the lake zone where the
ground motion was amplified to such a considerable extent by the lake- bed
clays. It is beyond doubt that, had there been to high-rise structures on the
lake bed, the amount of damage experienced during the earthquake would
have been drastically reduced.
The sensitivity of high –rise building to low-frequency seismic energy
emanating from a distant earthquake source is something that is becoming if
increasing relevance and concern. Not least of all this is because there has
been, in recent years, a dramatic increase in the number of high –rise cities,
many of which are situated in seismic belts or along their margins. The
increased (building) elevation of cities means that some of may start to “feel”
earthquakes and experience earthquake damage for the first time in their
history. Others, such as Maxico City, will find themselves increasingly
vulnerable to larger and more frequent losses than those experienced in the
past.
Building – Subsoil Interaction
The resonance coupling experienced in Maxico City between
earthquake shock waves, lake-bed clays and medium to high-rise buildings,
highlights the importance in seismic regions of trying to relate the dynamic
characteristics of a building to those of the subsoil on which it is situated.
The vulnerability of a structure to damage is considerably enhanced if the
nature frequency of vibration of a vibration of the subsoil and that of the
structure coincide.
In that context, although the lake-bed clays of Maxico City represent
an extreme example, many of the world’s major cities stand upon subsoil
conditions. These often comprise unconsolidated sediments, occasionally
water-saturated, associated with river valleys or coastal plains (i.e. area that
nave provided the natural resources needed to sustain large sedentary
populations). In many cases, however, the possibility of earthquake
resonance couplings of the type experienced in Maxico City has not yet been
examined.
District Disaster Management Plan, New Delhi
29
Earthquake Recurrence
The result of an analysis of the distribution of epicentres of major
century earthquakes in Maxico. The Central American Trench delineates a
plate boundary, formed where the Cocos Plate (to the south-wast) is
subducting beneath the much larger North American Plate (to the north –
east). The trench forms part of the so-called pacific “ring of fire,” and is one
of the most active plate boundaries in the world. Recurrence intervals for
large earthquakes along any given section of the trench vary, but alter
between 32 and 56 tears on average. However, the section that generated
the 1985 earthquake was one that had not experienced a major seismic event
for a much longer time period. It formed part of a well- known seismic gap,
the “Michoacan gap.” Gaps of this type in recorded seismic activity can
sometime be taken to indicate a greater risk of large earthquake occurrence,
because stresses and strains caused by plate movement have been able to
accumulate for a ling tine without release. Considerable attention in Mexico is
now focussed on the Guerrero seismic gap, which lies to the southeast of
1985 rupture.
This type of analysis id invaluable in helping to delineate the
distribution of earthquake hazard and risk in a region. It often serves to
identify spatial and temporal patterns in earthquake activity that can be used
as a basis for predicting, in general terms, the potential for major seismic
activity.
Catastrophic Loss
A final major lesson from the Mexican earthquake concerns the
dangers associated with the over-concentration of people and investment in
seismic areas. All other considerations being equal, the larger the number of
people and grater the economic wealth in earthquake regions, the greater the
potential for catastrophic loss. These influences are compounded in many
Third World regions by a lack of capital to invest in hazard assessment and
mitigation measures. Indeed, it is the combination of high hazard exposure,
over-concentration of people and economic investment, and effects of a
crippling national debt of that serve to make Mexico City the world’s
archetypal vulnerable city. The city and its metropolitan area accommodate
roughly 18 million people (over 20% of the total population of Mexico) in only
0.1% of the nation’s land area. Furthermore, the population of the city is
continuing to increase at an alarming rate (projected average growth rate for
1985-2000of 2.56% per annum) and will exceed 24 million by the year 2000.
Surrounded by shanty towns and slums, the city serves to symbolise all the
danger of uncontrolled urban growth.
Cities of this type are unfortunately becoming characteristic of many
parts of the Third World, where urban primacy on a grand scale is now a
severe problem. In the mid- 1980s the United Nations listed 34 metropolitan
areas with populations greater than 5 million, of which 22 (65%) were in
the Third World By the year 2025 they estimate that 93 cities, will exceed
this size, the majority of them (86%) in the Third World From the work of
Bilham (1988) it can be determined that of these rapidly expanding Third
District Disaster Management Plan, New Delhi
30
World cities, approximately 41% are within 200km of the location of a major
historical earthquake (associated with fatalities in excess of 9000) and /or a
plate boundary with the potential to generate magnitude 7.0 earthquakes.
Clearly, it is only through concerted international co-operation that the lossinfliction potential of future earthquakes in these areas can be reduced to
levels that are socially and economically acceptable.
Probably the only positive aspect of natural catastrophes such the only
positive aspect of natural catastrophes such as the 1985 Mexican earthquake
is that they provide an opportunity to acquire data that otherwise would be
unobtainable. These data should then be incorporated into hazard and risk
assessments and used as a basis for implementing measures aimed at
reducing the impact of similar events in the future. In that context, major
lessons from the Mexican earthquake include the following:
The disaster emphasized that high rise buildings are often sensitive to
earthquake over much greater distance than low rise ones. This has
important implications in view of the ever increasing number of “skyscraper”
cities around the world. It suggests that earthquake hazard and risk
assessments now need to consider the threat posed to cities many hundreds
of kilometres away from the most active seismic belts.
The disaster highlighted, once again the influence that subsoil conditions
exert on the severity of the earthquake hazard, and emphasised the need for
detailed examinations of the geological conditions underlying all major cities
in seismic zones.
It furnished new information concerning building vulnerability to earthquake
ground motions. Vulnerability varied considerably according to type and
height of construction, and the nature of the underlying subsoil. The findings
emphasise the importance in seismic regions of trying to relate the dynamic
characteristics of a building to those of the subsoil on which it is situated.
The vulnerability of a structure to damage is considerably enhanced if the
nature frequency of vibration of the subsoil and structure coincide.
The earthquake emphasised the value of analysis of the earthquake histories
of seismic regions. Analysis of this type may reveal spatial and temporal
patterns in earthquake activity that can be used as a basis for evaluating
seismic potential.
The earthquake served to reiterate the danger associated with the over
concentration of people and economic investment in areas that are exposed
to severe natural hazards. This is of particular relevance to many of the
rapidly urbanising countries of the Third World, where concerted international
effort is now required to stem escalating vulnerability to loss.
District Disaster Management Plan, New Delhi
31
INTENSITY SCALES
The Modified Mercalli Scale (MM) of 1931
Intensity I
Not felt except by a very few persons under especially favourable
circumstances.
Intensity II
Felt only by a few persons at rest, especially on upper floors of
buildings. Delicately suspended objects mat swing.
Intensity III
Felt noticeably indoors, especially on upper floors of buildings, but
many people of not recognize it as an earthquake. Standing motor cars may
rock slightly. Vibration like passing of truck. Duration estimated.
Intensity IV
During the day felt by many.
Earthquake Profile of Delhi
Delhi has been a witness to earthquakes in past. As per Iyengar
(2000) damaging earthquakes have occurred around Delhi since ancient
times. He points out that the great epic, Mahabharata mentions about
earthquakes during the war at Kurukshetra (Circa 3000 BC). More recently,
damage to Delhi in the 1720 earthquakes (intensity IX in Delhi) is well
discussed by Kafi Khan (Iyengar, 2000). Tandon (1953) mentions of damage
to the Qutab Minar during the 2803 earthquake near Mathura.
Srivastava and Roy (1982) discuss several more earthquakes in Delhi
region. These include: (a) earthquake of year 893 or 894 (Intensity XI XII)
which took place not far from Delhi in which many persons died; (b)
earthquake of 22 March 1825 near Delhi Intensity VII; earthquake of 17 July
1830 near Delhi (Intensity VIII); and (d) earthquake of 24 October 1831 near
Delhi (Intensity VI)
Delhi has also sustained earthquake damage in more recent times. For
instance, Srivastava and Somayajuluy (1966) mention of (a) Khurja
earthquake (M6.7) of 10 October 1956 in which 23 persons were killed in
Bulandshahr and some injured in Delhi; (b) M6.0 earthquake of 27 August
1960 near Delhi wherein about 50 persons in Delhi were injured; and (c) an
earthquake near Moradabad on 15 August 1966 that killed 14 persons in
District Disaster Management Plan, New Delhi
32
Delhi. Iyengar (2000) also mentions about damage to one of the minarets of
Delhi's Jama Masjid during the M4.0 earthquakes on 28 July 1994.
Most recently, the 1999 Chamoli earthquake (M6.5) took place about
280 km from Delhi. Such a moderate earthquake does not normally cause
damage at such large distance. And yet, several buildings in Delhi sustained
non-structural damage possibility due to peculiar geological and geotechnical
features if this area.
Only recently in the Month of march to May 2004 minor tremors
ranging from 1.6 to 3 on Richter scale have rocked the capital, reminding
once again Delhi’s susceptibility to earthquakes.
Past Earthquakes in and Around Delhi
15 July 1720 - New Delhi, Delhi, M7.6 (GSHAP Catalog)
28.66N, 77.25E
The last major earthquake in the New Delhi region. Heavy damage in the city.
4 April 1905 - Kangra, Himachal Pradesh, Mw7.8
00:50 UTC, 32.30N, 76.30E
This is the deadliest earthquake in modern Indian history. Close to 19,800 people
were killed and thousands were injured in the Kangra area. Most buildings were
destroyed at Kangra, McCloudganj and Dharamshala. Damage also extended into the
Dehradun area. Landslides and rockfalls occurred in the region. Damage was also
reported from many large cities in the Punjab, like Amritsar, Lahore, Jullunder and
Ludhiana. Felt over much of the northern sub-continent, as far east as Kolkata.
27 August 1960 - Gurgaon-Faridabad (Haryana), 6.0 (TS)
15:58:59.20 UTC, 28.20N, 77.40E
Damage from this earthquake extended into New Delhi where at least 50 people
were injured. Structural damage was reported in Karol Bagh and cracks in houses in
RK Puram.
20 June 1966 - Delhi-Gurgaon Border (Delhi-Haryana Border region), 4.7Mb
(ISC)
13:42:57 UTC, 28.50N, 76.98E, 53kms depth
29 July 1980 - Western Nepal, Mw 6.8 (HRV)
14:58:40 UTC, 29.60N, 81.09E
Between 150 - 200 persons were killed and hundreds injured. Extensive damage in
several towns in western Nepal. The quake also caused damage in Pithoragarh area,
nearly 50 kilometres away from the epicentre. 13 persons were killed here and 40
were injured. The quake was felt as far away as Kathmandu and New Delhi.
21 October 1991 - Near Pilang (Uttarkashi District), Mw 6.8 (NEIC)
21:23:14 UTC / 02:53:14 IST, 30.78N, 78.77E
Between 750 to 2000 people killed in the Gharwal region. It was also felt very
strongly in Uttar Pradesh, Chandigarh, Delhi, Haryana and Punjab. Some minor
damage was reported in Chandigarh and New Delhi.
District Disaster Management Plan, New Delhi
33
12 November 1996 - Near Kurukshetra (Haryana-U.P. bdr. region), 4.5 Mb
(NEIC)
04:20:58.0 UTC, 29.928N, 77.207E, 55.50ksm depth
4 May 1997 - Rothak-Sonepat Districts (Haryana), 4.1ML (EIDC)
07:19:22.0 UTC, 28.984N, 76.588E, 28.80kms depth
30 March 1998 - Mahendragarh-Bhiwani Districts (Haryana-Rajasthan Bdr.),
5.0Mb (NEIC)
23:55:45.0 UTC, 28.211N, 76.240E, 10kms depth
22 March 1999 - North of New Delhi, (Haryana-Uttar Pradesh Border
region), 4.1Mb (NEIC)
09:56:16.0 UTC, 29.257N, 76.94E, 207.60kms depth
29th March 1999 - Near Gopeshwar (Chamoli District), Mw 6.5 (HRV)
19:05:11 UTC, 30.492N, 79.288E
115 people killed in the Gharwal region. The quake was felt very strongly in Uttar
Pradesh, Chandigarh, Delhi and Haryana. In Haryana, one person was killed in the
city of Ambala and 2 at Nakodar in the neighbouring state of Punjab. Minor damage
to buildings in New Delhi, most significantly in Patparganj. Minor damage also
reported from Chandigarh.
28 April 2001 - Sonepat, M3.8
Felt widely in the New Delhi area and resulted in widespread panic in the city.
LARGEST INSTRUMENTED EARTHQUAKE IN HARYANA & DELHI
27 August 1960 - Gurgaon-Faridabad (Haryana), 6.0 (TS)
15:58:59.20UTC, 28.20N, 77.40E
Damage from this earthquake extended into New Delhi where at least 50 people
were injured. Structural damage was reported in Karol Bagh and cracks in houses in
R.K. Puram. (Source: www.asc-india.org)
Seismo - Tectonic Mapping
The situation necessitates the development of a microzonation map of
District New Delhi and its surroundings using state-of-the-art probabilistic
seismic hazard analysis (PSHA) methods. In a recent study by R. N. Iyengar
and S. Ghosh (Microzonation of earthquake hazard in Greater Delhi
area, Current Science, VOL. 87, NO. 9, 10 NOVEMBER 2004) seismio-tectonic
characterization has been attempted with India Gate in New Delhi as the
centre, a circular region of 300 km radius has been assumed as the
catchment area for Delhi city. Tectonic features around Delhi city discussed
by Valdiya, K. S., (Himalayan transverse faults and folds and their parallelism
with subsurface structures of north Indian plains. Tectonophysics, 1976, 32,
353–386) have been further improved to map all known faults in a radius of
300 km around Delhi city. Twenty faults, movement on which can cause
ground vibration at Delhi, are shown in Figure below.
District Disaster Management Plan, New Delhi
34
Source: CURRENT SCIENCE, VOL. 87, NO. 9, 10 NOVEMBER 2004
Microzonation Map
PSHA (Probabilistic Seismic Hazard Analysis) incorporates all known
faults, epicentres, past data and local characteristics in a judicious manner to
arrive at site seismic hazard. The soil conditions in the metropolitan area
can be summarized in the following manner: ‘The depths to bed rock vary
from near surface in Link Road, Pusa Road, Vijay Chowk, Daryaganj areas to
as deep as 40 to 60 m in the Patel Road, Lal Quila, Rajghat areas, 80 to 100
m in the Aurobindo Marg–IIT area and 150 m in the Yamuna river bed area.
The bedrock topography, in general, is undulating, characterized by several
humps and depressions. In the North Delhi area, the depths to bedrock east
of the ridge vary from near surface to 30 m, with a gradual easterly slope
towards the river Yamuna. West of the ridge in the Mall Road–Imperial
Avenue sections, the depths vary from near surface to 30 m and more, with
an abrupt deepening to 90 m in the north to as much as 200 m in the
Roshanara garden area in the south. In the Sabzi Mandi, Rani–Jhansi Road
area the bedrock occurs at shallow depths and at more than 20 m in the
Chandni Chowk Sadar Bazar-Lal Quila areas. The bedrock is overlain mostly
by clay in the North Delhi, Aurobindo Marg, and Yamuna river bed areas with
indications of sand/ silt with kankar and granular zones at several places.
District Disaster Management Plan, New Delhi
35
Pockets with high rise buildings or ill-designed high-risk areas exist
without specific consideration of earthquake resistance. Similarly, unplanned
settlements with sub standard structures are also prone to heavy damage
even in moderate shaking.
The Central Business District namely Connaught Place, numerous
District Centres and sprouting high rise group housing schemes are high risk
areas due to the vertical as well as plan configurations. The walled city area,
the trans-Yamuna area, and scattered pockets of unplanned settlements also
figures as high risk zones due to their substandard structures and high
densities
Issues
The city's settlement pattern has never been viewed in relation to location
and geological characteristics.
Pockets with high rise buildings or ill-designed high-risk areas exist without
specific consideration of earthquake resistance. Similarly, unplanned
settlements with sub standard structures are also prone to heavy damage
even in moderate shaking.
The Central Business District namely Connaught Place, numerous District
Centres and sprouting high rise group housing schemes are high risk areas
due to the vertical as well as plan configurations. The walled city area, the
trans-Yamuna area, and scattered pockets of unplanned settlements also
figures as high risk zones due to their substandard structures and high
densities. So far as housing is concerned, vulnerability analysis has never
been carried out and preliminary estimate of damages is not available for
strengthening of structures under normal improvement development
schemes.
The most recent Chamoli earthquake (29 March 1999) was felt all over Delhi.
There have been reports of cracks in a few tall buildings located on alluvial
deposits in the trans-Yamuna area.
Risk/ Vulnerability Analysis
Delhi, which is lies in Seismic Zone IV, is currently experiencing mild
seismicity. An earthquake of magnitude 7.0 on the Richter scale, that was
once considered hypothetical, is today a very real possibility. Keeping in view
the forecast of a major earthquake resistant design consideration, it has
become imperative to size up the earthquake scenario of the city and
increase awareness of earthquake resistant techniques. Considering areas
affected during past earthquakes of M - 6.5, it can be expected that such an
earthquake occurring in Delhi could adversely affect the whole of it with
damaging intensities and more than 50% of the Delhi Metropolitan Area - in
terms of probable damage scenario, earthquake would be the worst natural
disaster for Delhi.
District Disaster Management Plan, New Delhi
36
Hazard Due to Natural Features
Amongst the natural features the type of soil, topography and drainage
pattern is the most important factors that intensify or hinder the degree of
damage caused by the earthquake. Delhi’s soil type, drainage pattern and
geology depicts that the city is highly vulnerable to earthquake. Since a
large part of the district particularly the presidential house and the
surroundings are located on the ridge it can therefore be considered that
they might be less prone to damage during an earthquake.
Building Structure
Amongst the man-made features, the most important factor is the
building structure because if they are weak and susceptible the building
collapses leading to death of people in it. From the point of view of the
building structure the district New Delhi can be divided into 2 categories
Low rise bungalows build during British rule: The bungalows housing where
the most prominent people of the country live and the important offices are
also situated were build during the British rule. These constructions are note
only old but have crossed their age limit. These buildings therefore require
massive rehabilitation and retrofitting.
High rise commercial buildings: The high-rise commercial buildings need
assessment to ensure their earthquake resistivity.
The following DO’s and DON’Ts, if observed before, during and after an
earthquake, will definitely help in mitigation of the consequences of an
earthquake disaster:
Before an earthquake
Follow local building codes for earthquake resistant construction;
Advise retrofitting to ill – engineered or non-engineered or weak structures;
Encourage and participate in earthquake drills or training sessions;
Learn first – aid;
Identify medical centres, fire fighting stations, police posts or any other
organized relief society of your area in advance and establish contacts with
them;
Prepare family disaster mitigation plan for every household; and
District Disaster Management Plan, New Delhi
37
Every community should keep a record of persons, pets and cattle in each
house or working place making a special note of the aged and the infirm.
During an earthquake
Remain calm and reassure others;
Shut off electric mains and gas;
If indoors, do not run outside in panic, never use elevators or lifts;
If inside a building stand in a strong doorway or a corner or crawl, under a
strong bed or table;
Watch for falling objects like plaster, bricks, lighting fixtures, bookshelves
and other cabinets;
Stay away from glass windows, mirrors, chimneys and other projective parts
of the building;
If outside, avoid being close to high buildings, walls, power poles and other
objects that could fall. If possible move to an open area away from buildings;
and
If in an automobile. Stop away from bridges, flyovers, poles, buildings and
trees.
After an earthquake
Be prepared for ‘aftershocks’ which, although of less magnitude generally,
create damage by disturbing the precariously balanced debris;
Check for fires;
Check house for damages – evacuate if necessary;
Check for injuries – administer first aid, do not attempt to move seriously
injured persons unless they are in immediate danger of further injury; be
very careful in pulling partially buried persons;
Check service lines and appliances for damage. Do not use matches or
lighters until it has been established that there is no gas leak;
Never touch fallen power lines;
District Disaster Management Plan, New Delhi
38
Go round listen to sounds from persons buried under debris;
Wear shoes in all areas near debris and broken glass;
Cooperate with government authorities. Respond to requests for cooperation
and help from Government Authorities, Police and Fire Service;
Do not spread rumours, nor listen to rumours; and
Check for persons not yet accounted for.
Fire
Fire loss is national loss because what burns never returns. Fire is a
good servant, but a bad master. Amongst all hazards, fire and fire related
accidents carry a high degree of fire risk and pose a great problem. All fires
invariably cause loss of property both of private and government origin
besides causing loss of lives/injuries. Increased usage of electricity, LPG and
hazardous chemicals result in increase of the fire hazard potential. There is
need to have proper blend of inbuilt fire safety measures in building/premises
as per the specifications, there proper servicing and maintenance and also
the existence of well equipped public fire service which reduces the fire risk
to great extent. Fires are largely man-made disasters caused mostly by
negligence, poor maintenance or sabotage. The increased numbers of fire
accidents are mainly due to lack of fire safety norms including various
aspects like storage of inflammable material in godowns and enforcement
measures.
Characteristics of Fire
Frequently we come across the horror of fire, but by understanding fire
we can know its true nature and prepare our families and ourselves. Each;
year many people die or are injured in fires, many of which could be
prevented. Fire is:
Fast: There is little time. In less than 30 seconds a small flame can gent
completely out of control and turn into a major fire. It only takes minutes for
thick black smoke to fill a house. In minutes, house can be engulfed
Hot: heat is more threatening than flames. The heat from a fire alone can kill
◦
◦
room temperatures in a fire can be 100 C at floor level and rise to 600 C at
eye level. Inhaling this super hot air will scorch the lungs. This heat can melt
clothes to your skin. In five minutes a room can get so hot that everything in
it ignites at once causing a flashover.
Dark: Fire is not bright but is pitch black. Fire starts bright, but quickly
produces black smoke and complete darkness. If you wake up to a fire you
District Disaster Management Plan, New Delhi
39
may be blinded, disoriented and unable to find your way around even in a
familiar place like your own home.
Deadly: Smoke and toxic gases kill more people than flames do. Fire uses up
the oxygen you need and produces smoke and poisonous gases that kill.
Breathing even small amounts of smoke and toxic gases can make you
drowsy, disoriented and short of breath. The odourless fumes can lull you
into a deep sleep before the flames reach your door and you may not wake
up in time to escape.
Urban fire can occur in public places like cinema halls or high – rise
buildings; oil deports; petrol pumps; gas godowns; chemical godowns;
religious places; industrial establishments like factories, etc. Scientific
analysis of all causes of fire reveal that human negligence is either
directly/indirectly responsible for almost all fire accidents. Indicative factors
contributing to the outbreak of urban fires are:
Electric Origin: Caused due to defective wiring, use of sub-standard
equipment, over loading, fluctuations in electric supply and illegal tapping of
electricity.
Careless Smoking: Caused due to careless disposal of burning cigarette or
beedi ends, match – sticks etc.
Oven/Kitchen Fires: Caused in kitchen and ovens due to careless and
negligent handling of LPG as fuel and kerosene stoves.
Naked Light: Caused due to careless and inattentive use of naked flames,
candles, oil lamps, etc.
Arson: Caused due to extremist activities, groups or faction rivalry, revenge,
malicious ignition, etc.
Other Causes: Caused due to gas leakage, sparks from machinery,
spontaneous combustion, sparks from welding, chemical reaction, explosives
and fire works, lightening, etc.
Fire in Delhi is a major cause for loss of property and life. If the
number of incidents of fires is carefully studied area wise in Delhi Connaught
place is one of the places from where maximum percent of calls of fire
incidents have been received if we analyze the causes of maximum number
of fires in Delhi 70 percent of calls are due to electric short circuiting. This is
alarming because a single cause can be disastrous to life and property that
major investments are required mitigating these risks. Over the years the fire
accidents have also increased in places like Connaught Place, due to
District Disaster Management Plan, New Delhi
40
uncontrollable increase in congestion. In places where a better control can be
exerted there has been a visible reduction in fire accidents, for example
Rashtrapati Bhawan.
Issues
High population density, crowded streets, unmatched mix of occupancies,
inadequate water supply, poor electrical services, encroachment are few
examples of ineffective planning which adversely affect the fire response
time. Under the present circumstances, a response time of 3 minutes in
urban areas and 5 minutes in rural areas is
very difficult to achieve.
City administration has mainly concentrated on
fire fighting rather than fire prevention
Implementation of fire prevention regulations
is poor.
Evacuation plans in most buildings, schools,
colleges, offices are not prepared and hence
lead to increase in casualties due to stampede
in a major fire.
District Disaster Management Plan, New Delhi
41
Assessment of Risk
Fire risk in the district is more prominent in the following areas.
Risk in multi-storey buildings used as office premises: the risk is primarily
due to congestion, low maintenance, high frequency of visitors.
Risk in JJ Clusters: Many JJ Clusters in the district were removed in the year
2004 as per the High court Order. JJ Clusters by the virtue of the material
used in the construction are prone to frequent fire hazards. Them illegal
storage of flammable materials and other such activities increase the
probability of fire tremendously.
If we look at the breakup of fire accidents according to the type of
building Occupancy, it is clearly seen that major fires break out in industrial
and residential areas only. However fire in high rise building in places like
Connaught place can cause more damage to property and hence cause more
financial losses.
Nuclear Disasters
Disasters occurring due to direct consequence of exposure of
communities to nuclear hazards can be termed as Nuclear Disasters. Nuclear
Disasters are the high-risk but low probability disasters attendant with the
advancement in nuclear science and technology. The nuclear accidents can
affect large areas often crossing international boundaries.
Causes of Nuclear Disasters
Nuclear Disasters can essentially occur in two ways.
First of all due to deliberate actions, which include:
Use of nuclear weapons against civil population during a war or conflict.
Use of nuclear radioactive material by terrorists who seem to be adopting newer methods to
further their cause by violence as a tool to cause disturbance in societies. The attack on
Twin Towers, in New York on 09.09.2001, indicates that terrorists are no more reluctant or
even hesitant to cause mass causalities. To that extent, use of nuclear material by terrorists
is now in the realms of possibility.
Secondly, the impact of Nuclear Disasters are seen due to accidental release
of nuclear radiations, as mentioned below:Accident at Nuclear Power Plants Resulting in release of nuclear radiations.
Loss or theft of radioactive material from the facilities using nuclear material
for application in research and development, medicines, industry, etc.
District Disaster Management Plan, New Delhi
42
Transportation accidents, which involve nuclear material.
Improper or deficient disposal of radioactive waste material.
Possibilities of Nuclear Disasters due to use of Nuclear Weapons are very
remote because of various international treaties and ongoing Nuclear
Disarmament Movement and above all due to the deterrent nature of the
consequences. There is, however, a relatively greater possibility of Nuclear
Disasters occurring due to accidental causes or terrorist actions.
Chemical Disasters
By definition, Chemical Disasters simply implies a disaster caused by
chemical hazards.
Causes of Chemical Disasters
A Chemical Disaster may take place due to anyone or more of the
following:
An accident or explosion at the production facility of hazardous material.
An accident at the storage facility of hazardous material.
An accident during transportation of hazardous material through population centres.
Inadequacies in toxic waste management. This results in long-term health effect on
communities. Toxic waste can cause environmental pollution as well as ground water
pollution.
Failures in safety systems of chemical plants.
Deliberate sabotage of a manufacturing area or storage facility of a hazardous chemical
substances or a sabotage during transportation of such substance.
Occurrence of natural disasters, such as, earthquakes, cyclones, etc. can also trigger
chemical disasters essentially through damage and destruction to chemical industrial units
storing or producing hazardous material.
Chemical Terrorism
Chemical Disaster can also be caused due to indiscriminate use of
chemical warfare agents by terrorists. Such chemcial agents include sarin,
chlorine, sulfur, mustards, hydrogen, cyanide and VX, etc.
Impacts
Chemical Disasters lead to serious and varied impacts. These can result into
explosions and/or fires. The most hazardous impact of a chemical disaster
lies in the extreme pollution of air, water and food chain upto life-threatening
District Disaster Management Plan, New Delhi
43
levels even. The long term health impairment can even extend to coming
generaitons.
A chemical disaster into one or all of the following:Physical Damage: This includes damage or destruction of structure and
infrastructure. A transportation accident may damage the means of transport
used for transporting hazardous material viz. vehicle, rail, etc. Industrial fire
if not contained, may affect large areas.
Casualities: Chemical disaster may result in large scale casualities. While
quick medical relief is essential to save lives, immediate disposal of dead
bodies will also need planning.
Environmental Damage: Chemical Disaster affects the environment
because of likely contamination of Air, Water supply, land, crops,
vegetation and animal life. In some cases certain areas may become
uninhabitable for humans and animals. The possibility of mega scale
migration/evacuation/resettlement could loom large.
Biological Disaster
Biological Disaster has co – existed with human society since primitive
days. With rapid advancement in medical sciences and prevention and
social medicines, the impact and frequency ofsuch disasters have
reduced to some extent in advanced countries.
A biological disaster is the disaster which causes sickness fatalities in
humanbeings and animals at large scale, when they come in contact
with biological hazard in form of living organism such as, bacteria,
virus, fungi, etc. Destruction of crops and plantation also false within
the ambit of biological disaster.
All communicable diseases, either of humanbeings or livestock are
potential biological disaster. They spread widely, affect huge number
of people in communities, sometimes across the geographical limits of
provinces and nations.
Factors contributing to vulnerability to biological disaster
In Delhi, urban, semi urban and rural population all are vulnerable to
biological disasters, though for different reasons and in varying
degree. Some of the factors uniformly applicable are:
Population Growth: Leading to substandard and unhygienic living
condition, presenting a perfect condition for epidemic to set in.
District Disaster Management Plan, New Delhi
44
Poverty: A logical consequence of over population limits the capacity of
individuals and communities to limit or nullify the impact of epidemics.
Lack of rapid response epidemic control and containment mechanism:
Paucity of medical resources coupled with geographical location and
problems of communication make communities in rural areas
comparatively more vulnerable.
Low public awareness: Lack of basic health and hygiene education and
in some cases superstitions add to vulnerabiltiy of certain sections of
population.
Poor heatlh and malnutrition: Poor heatlh and malnutrition lead to
depleted body resistance to diseases. Thus, certain groups in urban
areas, and women and children in backward rural areas become more
vulnerable.
Poor state of health care system: Callous approach to public health
and safety coupled with meagre resources at the disposal civic bodies
at all levels also contributing to enhancement of vulnerability to
biological disasters.
Congestion in urban areas: Congestion in urban areas leads to problem
of waster disposal, which provides fertile ground for vaious diseases to
spread.
Bioterrorism: Ignorance towards emerging threats of bioterrorism, in
general, enhances the vulnerability.
Modern means of transport and communication: It is a paradox that
modern means of transport and communication have made the world
shirnk, which also add vulnerability to communicalbe diseases because
of frequent travel and greater social mixing.
Biological Disasters: Casual Phenomenon
Communicable diseases leading to biological disaster often erupt and
spread due to poor and unhygenics living conditions of individuals and
families within communities. The general living conditions and state of
medical services coupled with awareness levels of individuals also
determine the vulnerability of individuals and communities tobiological
hazards. It is very natural, therefore, that affluent communities are
less vulnerable to biological hazard as compared to poor communities.
Causes for epidemics and pandemics may be generalized as under:
Congested living
arrangement.
areas
with
inadequate
District Disaster Management Plan, New Delhi
hygiene
and
sanitation
45
Movement of infected personnel to non-epidemic areas. In case of
malaria, for example, the mortality rate in epidemeic regions is very
high duridng first two years of life. In groups from non-epidemic areas
who move in epidemic regions, all individuals run the risk of
developing severe form of malaria.
Malnutrition, particularly among children.
Ecological changes conducive to breeding of vectors.
Poor or insufficient water supply system, leading to consumption of
contaminated water, leading to water born diseases.
Poor health serivces and lack of programmes for immunisation and
vector control.
Terrorist Attack (Chemical And Biological Attacks, Bomb Threats)
Delhi being the power house of the
country is a target for terrorists. Is has faced
many a bomb attacks and threats that has
caused lots of damage to the life, property and
sentiments of the city. New Delhi District in
particular is place for the President, the Prime
minister, the Parliament house, the Supreme
Court, the High court, and other central and
state government offices. Therefore the threat
always looms on the city from the terrorist
elements.
Issues
Threat of terrorist attack looms large constantly over the district.
Therefore there is a need for preparedness in this regards a preparedness
that includes
Awareness amongst common people about what to do in such a situation.
Provision of safe shelters distributed in the district
Awareness about the safety provisions in chemical or biological attack
situations.
Resource Inventory/Capacity Analysis
District New Delhi has been struggling to decentralize administration
and increase people’s participation in various levels. To take part in this
District Disaster Management Plan, New Delhi
46
effort, regular Bhagidari meetings are held with prominent RWA
representatives. The active participation of RWAs is still lacking in this
district.
To serve as safe shelters, the district New Delhi has a large number of
gardens and round-about(s). The schools in this area also provide open
spaces and accommodate a large number of people.
The capacities of all the stake holders are being developed. Training
programmes have been organised for the Principals, teachers, masons,
engineers etc. Apart from these programmes, the communities are also being
made aware about their responsibilities at the time of disaster. The capacity
of community is critical, since they are the first responders to any incident or
mishap.
District Disaster Management Plan, New Delhi
47