Disasters threaten sustainable economic development worldwide. In the past twenty years, earthquakes, floods, tropical storms, droughts and other calamities have killed around three million people, inflicted injury, disease, homelessness, and misery on one billion others, and caused damage worth millions of rupees. Disasters destroy decades of human effort and investments, thereby placing new demands on society for reconstruction and rehabilitation.

Some of the major disasters that have occurred so far in this decade are as follows:

Number

16

29

70

64

Economic Losses

48.4

93.0

147.6

404.4

Insured Losses

6.5

10.9

29.8

98.8

The member states of the United Nations General Assembly declared the 90s  as the International Decade for Natural Disaster Reduction (IDNDR). This international promotional mechanism was conceived to run from  1990 through 1999, to motivate concerted international action and cooperation which could  “reduce the loss of life, property damage, and social and economic disruption caused by natural disasters, especially in developing countries”.

IDNDR is based on the understanding that there is sufficient scientific and technical knowledge, save lives and property  from natural and similar disasters through to more extensive application. IDNDR provides a framework and serves as a catalyst for disaster reduction. It provides a stimulus to provoke the expanded use of practical measures for more effective disaster preparedness and management practices.

The international impact of the subject was expanded in May 1994 at the World Conference for Natural Disaster Reduction, convened by the UN in Yokohama, Japan. Representatives of 155 nations adopted fundamental guidelines for natural disaster prevention, preparedness and mitigation, embodied in the Yokohama Strategy and Plan of Action for a Safer World. The Yokohama Conference underlined the importance of an economic rationale for disaster reduction, complementing the earlier scientific foundation with an essential commitment from public policy authorities.

The goals established at the start of IDNDR  are as follows:

·        To improve the capacity of each country to mitigate the effects of natural disasters, in the assessment of disaster damage potential, and in the establishment of early warning systems and disaster resistant capabilities.

·        To devise appropriate guidelines and strategies for applying existing scientific and technical knowledge.

·        To foster scientific and engineering endeavour aimed at addressing critical gaps in knowledge.

·        To disseminate existing and new technical information.

·        To develop measures for the assessment, prediction, prevention and mitigation of natural disasters through programmes of technical assistance and technology transfer, education and training, and to evaluate the effectiveness of programmes.

In essence, the decade's activities seek to shift the emphasis from post-disaster relief to pre-disaster risk reduction.  The key tasks in risk reduction are:

·        Avoiding habitation in hazardous areas;

·        Developing structures resistant to the onslaughts of hazards;

·        Developing the ability to rapidly evacuate hazardous areas or to shift residents to hazard-resistant structures;

·        Reducing or eliminating natural hazards through technological intervention (e.g., dams, plantings, beach groins); and

·        Establishing, through preparedness, the means to quickly recover from disasters with minimal additional suffering and loss of life.

At the local level, in Maharashtra, the experience of the September 30, 1993, earthquake near Killari, highlighted the need for a more comprehensive disaster management program at the state level.

Response to disasters, in the absence of a defined plan, would be arbitrary, leading to overemphasis on some actions and  absence of other critical actions.  The objectives of  any disaster management plan should be to localise a disaster, and to the maximum extent possible, contain it so as to minimise the impact on life, the environment and property. A formal plan for managing disasters is therefore necessary. It therefore includes a plan of action for the following disasters : earthquakes, floods, cyclones, epidemics, industrial and chemical accidents, road accidents and fires. At the same time disaster management plan has a strong mitigation aspect as well, which will reduce the frequency of occurrence of such disasters.

The plan would include  :

a.       Pre-planning a proper  sequence  of  response actions;

b.      Allocation of responsibilities to the participating agencies;

c.       Developing codes and standard operating procedures for various departments and relief   agencies involved;

d.      Inventory of existing facilities and resources;

e.       Mechanisms for effective management of resources; 

f.        Co-ordination of  all relief activities  including those of NGOs to ensure a coordinated and  effective response;

g.       Co-ordination with the state response machinery for appropriate support;

h.       Monitoring and evaluation of actions taken during relief and rehabilitation.

Planning for a disaster or emergency is a complex procedure since disaster are largely unscheduled. Emergency planning can be considered as  a process of preparation for a range of possible disasters and will include :

·        Identification and analysis of the potential hazards, and if possible the mitigation or elimination of their consequences;

·        Analysis of the resources available to cope with any potential disaster; and

·        Post - disaster response and recovery planning.

The primary purpose of emergency planning is the anticipation of   problems and development of  possible solutions within existing constraints. Basically the process includes :

·        Analysis of hazards which would include vulnerability and risk assessment of available resources;

·        Identification of necessary post - disaster tasks and allocation of these tasks to organisations and individuals;

·        Co-ordination of  all responding groups to ensure a cohesive and effective response.

The purpose of preparing this plan is :

·        To understand the vulnerability of the various districts to disasters;

·        To ascertain the status of existing resources and facilities available with the various agencies involved in disaster management in the state;

·        Assess their adequacies in dealing with a disaster;  and

·        Identify the requirements for institutional strengthening, and capacity strengthening of human resources. 

 Using this information, a rational basis for strengthening of the present system for management of disasters in the State of Maharashtra can be developed.

With this in view, a brain - storming workshop was held in May 1995, with the state department, experts, local officials, academic and research institutions and NGOs   who had experience in dealing with disaster situations. The workshop recommended that the GOM engage a small team of international and national consultants to work in concert with the GOM to prepare a Disaster Management Action Plan for the state and for selected districts. It was further proposed that a multi-disaster response plan should focus specifically on the following disasters – earthquakes,  floods,  cyclones, epidemics, road accidents, fires and industrial and chemical accidents.

1.1     Scope of the Study

This exercise of preparation of disaster management plan in Maharashtra, supported by the World Bank and UNDP, aims to develop a Disaster Management Action Plan (DMAP) for the state and all the districts. The study was  conducted in three phases as shown below.

Phase I - Document on Risk Analysis and Vulnerability Assessment for the state.

Phase II - Preparation of the State Disaster Management Action Plan and the District Disaster Management Action Plan for six districts, one from each division. Simultaneously, with  assistance from the UNDP, the exercise of preparation of District Disaster Management Action Plan with a uniform framework for the remaining twenty five districts is being  undertaken.

Phase  III - Document on Disaster Mitigation Strategy for State of Maharashtra.

The Disaster Management Action Plan for the state is proposed to be developed as an integrated plan encompassing all  disasters in the multi-response fashion keeping with the international trend. Albeit, a common planning and operational framework is proposed   for all the  disasters which  would  ensure a systematic assessment, communication and management of risk, appropriate for a disaster and identification of response.

During the first phase of the study, the Government of Maharashtra  appointed expert committees for deliberating on the various hazards. The committee meetings provided a platform for discussions on the current status of information related to existing emergency plans in the state, additional study requirements, possible approaches to be followed while developing the plan and a greater focus  on the scope of the study.

Following the meetings, these committees were dissolved and the project continued with more one-to-one  meetings between various experts and the national consultants appointed to undertake  the present assignment.

To obtain district level information  formats / templates of the information requirements had been prepared by the consultants and discussed with district collectors and divisional commissioners at a workshop held on 3^rd January, 1997, at the World Trade Centre, Mumbai. Based on the response to these formats and templates, risk assessment and vulnerability analysis exercise was undertaken at the district level by the Collectors through a series of consultative meetings. Co-ordinators were appointed to assist District Collectors for verification of information and collating data. The work of co-ordinators was facilitated by the support from Divisional Commissioner’s office through Divisional Co-ordinators appointed under the project.

The process of consultation subsequently continued through a series of meetings with district collectors and divisional commissioners at the district and divisional level. The draft documents were presented and reviewed at a workshop in Washington in June, 1997, by a group of experts, the World Bank, UNDP and DFID. Based on their suggestions, the documents were revised.

The scope of the present document extends to an analysis of the generic reasons for the risks due to hazards in the state, and an attempt at identifying the vulnerable areas in the state specific to each hazard.  Secondary data from the various state government departments and information from newspaper clippings has been sought. A detailed  review of the existing resources and their adequacy vis-a-vis disaster management entails collection of exhaustive information on the project status in the various districts. The major issues that emerged from the committee meetings are reiterated in this document for the sake of continuity.

“Sociologically, a disaster is a, event, located in time and space, that produces the conditions whereby the continuity of the structure and processes of social units become  problematic.” (Russell R. Dynes, 1980. Participation in Social and Political Activities, San Francisco, Jossey-Bass Publishers. )

 The developing countries where two thirds of the world’s  population live, suffer the most debilitating consequences due to natural disasters.   90  per cent of the natural disasters and 95 per cent of the total disaster  related deaths worldwide, occur in the developing countries. In the light of this data, it naturally becomes important to examine the connection between development and disasters, as also the link between poverty and disasters in order to develop appropriate rehabilitation and mitigation strategies on the one hand, and refinement of development strategies on the other.

Based on the events of natural disaster - those occurring  during the period of thirty  years from 1^st January 1963 to 31^st December 1992 - a global study was conducted to understand the impacts of disaster on populations.  The impact was understood mainly in three different categories  viz, no. of lives lost, number of people affected in compared to total population of the region and the significant damage, i.e. damage to the country in relation to its total annual gross national product (GNP).  The results of this study are presented below.  These results apply to the region of Indian peninsula and are presented in graphical forms.  

1.     Figure 1: The first figure shows the number of significant disasters which occurred in the region, for each of the three categories described previously, over the entire period, by five-year windows.  It thus shows the five-year period(s) which were particularly severe for the region as far as significant disasters are concerned, as well as the increase of such disasters  over time.

2.     Figure 2: The second figure takes the same data and gives a statistically calculated trend line for the number of significant disasters in each of the three categories over the  30 year period of the study.  It is thus an indication of whether  of significant disasters in each category can be expected to increase in number (and  at what rate), decrease or remain at the same level in the future based on 30 years of history in the region.

3.     Figure 3: The third figure shows the number  of significant disasters in each category which has struck the region over the past 30 years, along with a total of all such disasters in that category.

4.     Figure 4: The fourth figure shows the same data as a pie chart showing the proportion of  significant disaster in each category which the region has  suffered over the entire period.

5.     Figure 5: The last figure in each group shows the statistically calculated trend lines for  significant disaster in each category.  It is thus an indication of whether each type of significant disaster can be expected to increase in number (and at what rate), decrease or remain at the same level in the future based on 30 years of history in the region.

Note : Trends have usually not been computed for all types of significant disasters which have struck the region, but only for the principal ones i.e. only those which represent some 5-10 per cent or more of all such disasters for the region.  It should also be noted that because of the small number of samples of disaster types for some regions, the statistical confidence level of the calculated trends may not be high in those cases.

These figures indicate:

1.       An increasing trend in number of disasters over last thirty years from 20 disasters in 1963-67 to 65 disasters in the period 1988-92

2.       Number of deaths show an increasing trend over the last 30 years, except for minor fluctuations.  Number of deaths is quite high during the five years of 1988-92.  The increasing trend in number of deaths is much more evident in the  figure 2. 

3.       Number of persons affected due to disasters has not increased   as much as the number of deaths.  So the number of people who died is much more  than the number of people affected.

4.       ‘The significant damage’  (damage of one per cent or more of total annual GNP) does not show any  increasing trend over 25 years, 1963 to 1987.   However, the cumulative frequency in figure 2 indicates an increasing trend.   It shows that though the number of deaths  have increase, property damage and damage in  total annual GNP has not increase proportionately.  Over the five years of 1988-92, significant damage  has also increased to a large extent.  It also shows that the five years of 1988-92 were, really disastrous, having  higher number  of disasters more of deaths and  causing more property damage.

5.       Figure 3 and  4 show that floods are the most damaging disasters in terms of deaths, persons affected and damages, followed by tropical cyclones. 38 per cent of the deaths in disasters are due to occurrence of floods. Droughts also affect a large number of persons causing  migration and loss of employment but they do not kill many. 24 per cent of persons affected during disasters have been because of droughts.  Epidemics also take a huge toll of lives  but they do not cause significant damage to assets.  Earthquakes  are rated quite low in terms of their  damaging capacity but this may be because of infrequent occurrences of high magnitude earthquakes.  Figure 4 that shows that damage due to floods is more visible as  they account for  about 50 per cent  of significant damages.  54 per cent  people are affected due to floods and 36 per cent of total disaster related deaths are due to floods.  Tropical storms rate second as far as their damaging capacities go, followed by epidemics.

6.     Based on the trends shown so far, statistical analysis has been done to show expected      trends in disaster characteristics. Figure 5 shows that the significant damage may be increased in case of floods and tropical cyclones in future.  Earthquakes also may cause higher damages than before, however, increase in damage due to earthquakes is expected to be lower than  that by floods and storms.  It is expected that droughts will show reduced damages. However, the number of people  affected due to droughts will be increased.  The number of people  affected is expected to be quite high due to floods and  steady in case  of epidemics.  Interestingly, number of persons affected due to storms is expected to be few, which may be an indication of better predictability and efficient warning systems. The figure also indicates that number of deaths will increase  for floods and epidemics.  Whereas  deaths due to tropical storms will be reduced to some extent.

 7.  Assessments of the  future trends indicate  that natural events causing disasters will be more frequent with floods causing the  most severe disasters.

However, it must be noted that all the above discussions are not limited to India  but covers Afghanistan, Pakistan, Nepal, Bhutan, Bangladesh and Sri Lanka too.  There are differences among these countries in their geographical locations, topography and their  developmental status.  It also indicates vast differences in relative intensity of hazards that these countries face. 

The Economic and Social Commission for Asia and Pacific  report on “Natural Hazards and Natural Disaster Reduction  in Asia and the Pacific”  indicates that India has a moderate risk of facing cyclones and earthquakes, whereas it is severely prone to the risks of floods and droughts. (Table I)

Table I : Relative intensity of hazards faced by some countries/areas in Asia and the Pacific

Australia

S

S

L

S

Bangladesh

S

S

S

L

L

L

L

China

M

S

S

S

L

M

Cook Islands

M

L

S

L

L

M

Federated States of Micronesia

M

S^*

S

L

L

S

Fiji

S

S

M

M

S

S

Hong Kong

M

L

M

M

India

M

S

S

M

L

M

Indonesia

L

M

M

S

M

L

M

Kiribati

L

S^*

S

L

L

S

Lao People’s Democratic Republic

M

L

Malaysia

M

L

L

Marshall Islands

M

S^*

S

L

L

L

Myanmar

M

M

M

S

S

Nepal

M

M

M

M

M

Niue

M

L^*

M

L

L

M

Pakistan

L

S

M

S

L

L

Palau

M

M^*

M

L

L

M

Papua New Guinea

L

S

M

S

S

S

S

L

Philippines

S

S

M

S

M

M

L

S

Solomon Islands

S

S

L

S

S

S

S

L

Sri Lanka

M

M

M

S

L

Thailand

M

S

S

L

L

L

Tokelau

M

S^*

S

L

L

S

Tonga

S

M

M

S

S

L

S

Tuvalu

L

S^*

M

L

L

S

Vanuatu

S

S

L

S

S

S

S

L

Vietnam

S

S

L

L

L

L

Samoa

M

S

L

M

L

S

S

L

Source:            Asian Disaster Preparedness Center

                        DHA/South Pacific Regional Environmental       Programme/Emergency Management Australia

Legend:           S = severe; M = moderate: L = low

3.     Risk Assessment for the State of Maharashtra

“Risk is the probability that injury to life or damage to property and the environment will occur. The extent to which risk is either increased or diminished is the result of the interaction of a multitude of causation chains of events.” (Terry Jeggle and Rob Stephenson, Concepts of Hazard and Vulnerability Analysis).

The dominant physical trait of the state of Maharashtra is its plateau character. The state is covered by the Satpura range on its northern side while Ajanta and Satmala ranges run through the central part of the state.  The Arabian sea guards the western boundary of  Maharashtra with a coastal line of 720 kilometres. Gujarat and Madhya Pradesh form the state’s boundaries on its northern side with the latter also covering the eastern region while  Goa, Karnataka,   and Andhra Pradesh  are on the Southern side.      

The state receives its rainfall chiefly from the southwesterly winds. Normally, there are heavy rains  in the coastal region (around 2000 mm), scanty rains in the rain-shadow regions in the central part (around 500 mm) and medium rains in the eastern part of the state (around 1000 mm).

·        Area :  3,07,713 sq.Km

·        Number of administrative divisions  : 6

·        Number of districts  : 31

·        Number of talukas : 325

·        Number of city and town units :  336

·        Number of  inhabitated villages : 40,412

·        Total  population (census 1991) :  78,937,000

Maharashtra is the country’s leading industrial state, accounting for 23 per cent of the gross value output from the industrial sector. Its main areas of strength are textiles, pharmaceuticals, petrochemical industries, heavy chemical industries, electrical automobile industries, engineering and food processing. The state is a leading manufacturer of three wheelers, jeeps, synthetics, cold rolled steel products, industrial alcohol and plastic. Around 30 per cent of the sugar output of  the country is from Maharashtra. The organisational structure for the state is given in Appendix V. As a part of risk analysis, effort is being made to look at the available data and assess the possible risk for each of the hazards.

Of  all  natural hazards, earthquakes seem  the  most terrifying.   They  can inflict tremendous damage  within  seconds and  without warning at any time of day, on any day of the  year.  Ground  shaking and surface faulting are often just the  forerunners  of secondary damage, such as fires, floods (caused  by  dam bursts), landslides, quick soil and tsunamis (seismic sea waves).

Earthquakes  are  caused  by the movement  of  massive  land area called plate on the earth's crust.  Often covering areas larger  than the  continent, these plates are in a constant state  of motion, acted upon by the periodic forces of the solar system and movement caused by the rotation of the earth.  As the plates move in to relation  to  one another, stresses form and accumulate  until  a fracture  or  abrupt  slippage occurs.  This  sudden  release  of stress is called an earthquake.

The place at which the stress is released is known as the focus  of an earthquake.  From this point, mechanical  energy  is initiated  in  the form of waves that radiate in  all  directions through  the  earth.   When this energy arrives  at  the  earth's surface,  it  forms secondary surface waves.  The  frequency  and amplitude  of the vibrations produced at the surface,  indicating the  severity  of  the  earthquake,  depends  on  the  amount  of mechanical  energy released at the focus, the distance and  depth of  the focus, and the structural properties of the rock or  soil on or near the surface.

Earthquakes can occur anywhere. They may occur in an area  not known  to  have experienced previous activity and may  suggest  a temporary increase in  risk of  hazard in the area. Or they may occur in areas  which have a previous history of subterranean  sounds  and seismic activities.  Another important  indication  as to where  earthquakes  may occur  human activity like the construction of  a   reservoir. However,  it  may  be noted that some  of  the  physical phenomena causing earthquake are still poorly understood.

Earthquakes have several distinct effects that can damage structures, disrupt and even endanger our  lives.  An understanding of these natural hazards and how they result in damage can lead to more effective safety planning at the city level, and to better decisions about the uses of individual lots.

·        Ground Shaking is the most geographically widespread effect of earthquakes, occurring throughout the region.

·        Surface rupture may occur directly along the fault line.

·        Ground failure occurs when soil that is saturated with water, is on a slope,  is otherwise weak, cannot support structures, or even itself, after being subjected to ground shaking.

·        Other hazards that can result from earthquakes include tsunami and seiches.

Most earthquake damage is due to  ground shaking  which occurs in all earthquakes. The impacts of ground shaking will be quite widespread, and are much less predictable than those of surface rupture.  The severity of ground shaking varies considerably over the effected region, depending on:

·        the size of the earthquake;

·        the distance from the causative fault;

·        the nature of the soil at the site;

·        the nature of the geologic material between the site and the fault topography.

In general, sites with stronger soil will experience shaking of less intensity than those in low-lying areas. Some sites, particularly those with poor soils, will experience strong ground shaking even in distant earthquakes.  Sites with stronger soil will experience strong ground shaking only when a nearby fault is involved.

The most obvious and direct effect of earthquake  is the rupture of the ground surface along the fault.  Ground rupture occurs in some, but not all large earthquakes.  Structures are often not able to withstand surface rupture.  Streets, utilities and other lifelines that cross an earthquake fault are at great risk of damage.  The impacts of fault rupture, while locally severe, are not widespread and are relatively predictable. 

Ground failure means that the soil is weakened so that can it no longer support its own weight or the weight of structures.  The major types of ground failure associated with earthquakes are liquefaction, landslides  and settlement. 

In addition to the characteristics of the earthquake and of the site (such as the magnitude, duration, soils type), a structure's characteristics, including structural type, materials, design, and quality of construction and maintenance, will determine how well it will perform.  After San Francisco's 1865 earthquake, the front page of a local newspaper observed, "Well-built structures on good ground survived the shaking effects of the earthquake better than structures on made ground. It may be noted that  buildings having walls properly secured and lain in cement, with sound foundations, suffer the least damage during earthquakes.

There are other building types, in addition to unreinforced masonry buildings, that have not performed well in earthquakes.   The most serious hazard, and also the most difficult policy issues, may be posed by non-ductile concrete frame structures.  In many of these buildings, the frame was not designed or constructed to allow it to move without fracturing.  As a result, these are susceptible to collapse in strong earthquakes.  There were many falls of such buildings in the San Fernando 1971  earthquake.  Many deaths in the Mexico City 1985 ,  Armenia 1988,  Northridge 1994 and  Kobe 1995 earthquakes resulted from the fall of non-ductile concrete frame buildings.

“Soft-storey” buildings or those in which at least one storey often the ground floor has much less rigidity and/or strength than the rest of the structure, are significant hazards.  The 1974 Blume report identified smaller  wood-frame buildings with soft storeys as having the potential to collapse during an earthquake. During  both the Loma Prieta and the  Northridge 1994 earthquakes, soft-storey residential  buildings failed, resulting in deaths. Small wood-frame residential buildings can be very resistant to earthquake ground shaking, especially if they are bolted to their foundations and have strong first storeys.

Typically, in Latur, the housing material consisted of stone and mud resulting in total or sizeable loss of  houses along with the loss of nearly 8,000 people in the affected villages. The data on vulnerable houses is given in the vulnerability analysis.

The impact of earthquakes differ for urban and rural areas, primarily because of the nature of infrastructure, quality of housing and occupational differences. In rural areas, it is primarily the housing and physical structures (including irrigation infrastructure) which may suffer extensive damage, without necessarily destroying the crops.

In urban areas, in addition to housing and physical infrastructures, it may also disturb the service infrastructure such as water supply, sewage, telephones, electricity, piped gas supply etc., which are essentially underground installations and hence exposed to a direct impact. The disruption, therefore, in urban areas and consequent investments for rehabilitation becomes a major challenge. So, more emphasis  may  be given  on  mitigative and preparedness measures to  minimise  the disastrous effects of an earthquake.

Earthquakes’ most profound impacts are deaths and serious injuries.  Number of casualties largely depend on the number of people in the area at the time and the types of structures that they occupy.  Most deaths and injuries are caused by the failure of buildings and structures. The number of casualties also depend upon the time of occurrence of the earthquake.

Important variables could substantially reduce the toll.  The failure (or lack of failure) of a few high-occupancy or  critical facilities such as arenas, theaters, or dams could influence the final casualty count significantly. The degree of water saturation of the ground will influence the occurrence of landslides and the area subject to liquefaction.  Weather conditions, especially wind speed and direction, will affect the spread of fire and the ability of emergency responders to control fires.

During its evolution, the Indian peninsula was subjected  to intense  tectonic forces due to which numerous folds, faults  and fractures have been developed in the ancient rocks of this land mass.  peninsular  India is classified as  a  stable  continental region.

The earthquakes in a stable continental area, such  as the  one  at  Killari  on 30th  September  1993,  were  caused  by adjustments of crustal blocks along such pre-existing weak  zones.  Isolated seismic activity within the shield is indicative of  the movements going on along some of the old basement faults, perhaps at a very slow rate.

The state of Maharashtra and its adjoining areas form  part of  the peninsular shield of India.     The state of  Maharashtra occupies   the  central-western  portion  of  peninsular   India, technically  an intraplate continental area. Most of  Maharashtra is  covered  by  the deccan traps, a  sequence  of  basalt  flows placed about 65 million years ago.  In most of the area,  these flows   are  nearly  horizontal,  demonstrating   that   tectonic deformation  accumulated  is very little or nil.   Though  this  area was  treated as seismically stable with no potential for   disastrous  earthquakes, this belief was shattered by  the  Koyna earthquake of December 11, 1967, with magnitude of 6.5 on the Richter Scale. Recent Latur  earthquake  of September  30, 1993, having magnitude  6.4  which occurred  well  within the central part of the shield  led  to  a review of the seismic activity in the stable shield zone. 

Thus, tectonic stability in the deccan plateau may appear  to be  inconsistent  with the observed level  of  seismicity.   This apparent contradiction reflects the primitive stage of  knowledge about  seismogenesis  in stable continental region, and is  the root  of  problem  of rise assessment  of an earthquake. Thus the potentially  active tectonic features which could produce earthquakes with  engineering consequences need to be studied.

It may be noted that stable continental region  worldwide are characterized by  a very  large  number  of unknown faults that can  at  some  point produce  an earthquake.  Many of these faults may be  located  in areas  that  have  low  or  no  seismicity  and  are  technically stable.

Maharashtra and adjoining regions are prone to  earthquakes of  moderate  magnitude  as can be seen from the experience of  several  years.   Koyna regions experiences the maximum number of tremors in Maharashtra. Excluding the Koyna region, and other regions of Killari, Khardi (Bhatsa) and Medhi (Surya),  appendix III lists 137 earthquakes  of which 121 earthquakes of magnitude about 3.0 or above  are in Maharashtra and 16  are in the adjoining regions. Table II gives a list of the major earthquake occurrences  in Maharashtra.

Table II: Major Earthquakes in Maharashtra

The Deouskar committee report of 1995 presents the pattern of seismicity in Maharashtra. The above map indicates  the location of areas which have experienced earthquakes till date. The study reports  that :

·        Earthquakes  in Maharashtra show major alignment  along  the west coast and western ghats region.  Seismic activity can be  seen near Ratnagiri,  along the western coast, Koyna Nagar,  Bhatsa and Surya areas of  Thane  district.

·        The  north - south trend further continues  deep  inside  Gujarat.  The striking characteristic  of this narrow region is its  alignment  with the hot spring belt.  It appears that the  off - coast activity is associated with submerged faults along the west coast of Maharashtra.

·        In  north Maharashtra, the seismic activity near  Dhule,  Akola, Jalgaon  and  Amravati could be due to movements  on  the  faults present in the area associated with the complex system of Narmada, Tapi and Purna lineaments.  However, the exact seismic  status of these lineaments needs to be evaluated with extensive monitoring.

·        In north - east corner of Maharashtra, the earthquake activity  in  Nagpur  and Bhandara districts may  be  associated  with Deolapar thrust or sheared and faulted zones of Ramtek and Sakoli Basins.  This needs to be confirmed.

·        Isolated  activity  is seen near  Beed,  Nanded,  Ujjani  and Solapur  in eastern Maharashtra and  Uran, Kolhapur and Sindhudurga  in south-west Maharashtra.  These activities may be due to  movements on local faults in  the basement.  

·        Seismicity  is  also seen  near  Bhatsanagar  and  Suryanagar.  Recently,  isolated  activity also  occurred  in  Latur-Osmanabad districts in south-east Maharashtra.

Based on the earthquakes occurred so  far in the state and considering the seismic pattern, a rezoning, for new dam designs only, has been proposed  by the Deouskar Committee for the state of Maharashtra. The existing and the proposed zoning map  is  presented below.   It  may  be  noted  that  even   after   using sophisticated  techniques  like  carbon dating,  it  has  not  been possible to identify whether the fault is active. If some seismicity is associated with a  major lineament, it can be considered as an active tectonic feature for the  purpose  of  engineering seismic  risk  analysis  and  these regions can be considered as risk prone.

The  west  coast - Western Ghats seismogenic region is  the  most active  area in the Maharashtra state.  The Koyna-Warna  and  the Bhatsa areas are located in this region.  Even before the  occurrence of the Koyna earthquake of 11 December, 1967, with  magnitude 6.5,  earthquakes  with  magnitude of about 6.0 are  known  to  have occurred in this region. The report further observes that :

·        The  activity in the Koyna-Warna region  has  been  continuing  for the  past three decades with  occasional  spurts, producing events with magnitude above 5.0.  This trend is expected  to  continue in future. 

·        Bhatsa region experienced a swarm of seismic activity  during  1983-84, with  a  maximum magnitude of 4.9.  The activity  has  died  down since  then with only a temporary spurt in 1990.

·        The Surya area about 50 km. north-west of Bhatsa, has recently shown  increase in seismic activity.  The energy in  Bhatsa-Surya region  may  not have been fully released and possibility  of  an earthquake  with a magnitude of around 6.0 in future, cannot be  ruled out.

·        Further south of Warna, some micro seismic activity  has been  reported  in  the past. Because this region  lies  in  the active west coast-Western Ghats, the   possibility of a maximum magnitude earthquake of around 6.0 cannot be ruled out in future.

·        There was no evidence of any significant seismic  activity  in the  Latur-Osmanabad area in the known past.  Also,  the  tectonic features  to  which the Killari earthquake of 30  September,  1993, could be attributed are not known sufficiently.  However, the  occurrence of Killari earthquake of moderate magnitude of 6.4 gives an  indication  of   neotectonic  activity  in  the  area.  Though,  the stress has  been released at Killari,   a similar magnitude earthquake at some other place in the area cannot be ruled out.

·        Before  the Killari  earthquake,  infrequent  tremors  and subterranean sounds had been reported  in  the area.  Similar instances were also reported from many other  locations in Beed, Parbhani and Nanded districts.  In the absence of knowledge  about  any seismotectonic features in this  area,  low to moderate earthquakes can be experienced.

·        In addition to the above seismogenic regions in Maharashtra,  the  Narmada-Tapi  region covering the  border  areas  of Maharashtra  and Madhya Pradesh states  has been reported  to  be active  since historical times. Tense fracturing, alignment of  hot springs  and locations of epicenters in these areas leads to  the conclusion  that these two are the zones of crustal  weakness  in Maharashtra.

·        The  Tapi  and  the Purna lineaments in  the  northern  part  of Maharashtra have been recognized as active faults with  potential to   generate  low  magnitude  earthquakes. The   Tapi   lineament represents  a line of crustal weakness along which  activity  has been  recurrent  during  different  periods.  Earthquakes   above magnitude 6.0 are known to have occurred in the northern parts of this region across the border of Maharashtra.

·        According  to a scientist, there is a major anticipated  zone  of uplift  in the Sangola area and another to the east of  Sholapur.  Vertical  movements  of these crustal blocks  may  cause  seismic disturbances  in the areas, as  has happened in Killari .

·        Due to increasing trend of seismic activity noticed in Maharashtra in recent times, earthquakes with low  magnitudes around 4 to 4.5 may occur in areas where there has been no  seismic activity in the past.

While doing a risk assessment for  earthquakes, mention has to be made of  reservoir induced seismicity (RIS). The 1967 Koyna earthquake of 6.5 magnitude  is contended to be due to RIS.  Between 1963  to  1998, the Koyna region has faced  102715  tremors,  of which 79 were  above magnitude of 4 (Richter scale) and seven were above magnitude of  5 (Richter scale) as listed below.

 Table III: Intensity of Earthquakes in Koyna Region (1963 to 1998) on Richter scale