A sudden, transient motion or trembling in the earth's crust, resulting from the propagation of seismic waves caused by faulting of the rocks either at shallow and/or deeper depths is known as earthquake. The motion is caused by the quick release of slowly accumulated energy in the form of seismic waves. The release of accumulated energy may occur at any depth and time but the intensity of damage is directly proportional to the movement on a fault, which is a thin zone, both at vertical and horizontal plains, of crushed rock between two blocks of rock. A fault can range in length from a few centimeters to hundreds of kilometers. The larger the fault length, the larger the energy release by fault movements. The ground shaking and the radiated seismic energy are caused most commonly by sudden slip on a fault, or other sudden
stress changes in the Earth. Sudden break within the upper layers of the earth, sometimes breaking the surface, resulting in the vibration of the ground, where strong enough will cause the collapse of buildings and destruction of life and property. Based on long term historical records, about 18 major earthquakes (7.0 - 7.9 on the Richter scale) and one great earthquake (8.0 or above) are expected in any given year globally.
Any physical phenomenon associated with an earthquake that may produce adverse effects on human activities is termed as earthquake hazard. This includes surface faulting, ground shaking, landslides, liquefaction, tectonic deformation, tsunami, and their effects on land use, man-made structures, and socio-economic systems. A commonly used restricted definition of earthquake hazard is the probability of occurrence of a specified level of ground shaking in a specified period of time.
Similarly, earthquake risk is the expected (or probable) life loss, injury, or building damage that will happen, given the probability of earthquake hazard. Earthquake risk and earthquake hazard are occasionally used interchangeably.
Bangladesh, by and large, is seismically active. The occurrence of earthquakes with magnitude averaging around 5 in Richter scale is quite frequent especially in its eastern region. Although, Dhaka has not been experienced with any moderate to large earthquake in historical past, even then the earthquake of December 19, 2001 with magnitude of 4.5 and focal depth of 10 km located very close to Dhaka is certainly an indication of its earthquake source and vulnerability. In addition, micro-seismicity data also supports the existence of at least four earthquake source points in and around Dhaka. The earthquake disaster risk index has placed Dhaka among the 20 most vulnerable cities in the world. Dhaka with its population of around 13 million and enormous poorly constructed and dilapidated structures signifies extremely vulnerable conditions for massive loss of lives and property in the event of a moderately large earthquake.
The recently measured plate motions at six different sites of Bangladesh including Dhaka; (the research being jointly conducted by Lamont-Doherty Earth Observatory, Columbia University, USA and the Department of Geology, Dhaka University) clearly demonstrate that Dhaka is moving 30.6 mm/year in the direction northeast. Further, the rate of strain accumulation is relatively high in and around Dhaka. It may precipitate in an earthquake of magnitude 6.8 in the event of the release of accumulated strain. The shallow subsurface of Dhaka is also characterized by number of faults of variable dimensions. These faults are vulnerable to motion where these coincide with the zones of high particle velocity.
The coincidence of the zones of high particle velocity with the location of faults suggests that the western part of Dhaka city from Mirpur-Kalyanpur to Pagla along Buriganga river and the eastern part of Dhaka city from Uttar Khan-Badda to Demra along Balu river has emerged
as high risk zone. The peak ground acceleration in these areas has been calculated ranging between 0.3 to 0.35 if an earthquake of magnitude 5.6 occurs in and around Dhaka city. The resonant length in these areas suggests an optimal height beyond five stories; additional seismic factor needs to be introduced in addition to general seismic factor which is introduced based on seismic factors of the site specifically for earthquake resistant building code. The entire Dhaka megacity has been looked upon from earthquake hazard point of view. It has been divided into four zones of earthquake hazard vulnerability ranging between very high risks and low risk.
Earthquake cannot be prevented. But certainly it is high time to be much more concerned about the probable impending earthquake in order to minimise the loss of lives and property in national interest. On the basis of the above facts, we should develop earthquake monitoring
network in Bangladesh immediately. It is of prime importance to set a national institute of earthquake research to develop high skilled manpower that can perform the task for earthquake risk assessment and management. We should remember that one earthquake of moderate intensity would kill thousands of people and destroy enormous national property.
Death is certain for all human beings but painful death is not desirable.
Dr. Aftab Alam Khan, Professor, Geology Department, Dhaka University is Vice President, Bangladesh Earthquake Society (BES)
Experts predict the deaths of at least 96,000 people, injuries of 1,27,000 and the collapse of 28 percent of the existing buildings if a moderate earthquake hits the city. They told a workshop the direct loss would be worth a billion dollars in case of an earthquake of medium intensity.
Dhaka City Corporation (DCC) and Bangladesh Earthquake Society (BES) jointly organised the workshop on "Earthquake Preparedness and Management" last week to create awareness on earthquakes, sponsored jointly by Care Bangladesh and USAID.
Speaking as the chief guest, President of BES Jamilur Reza Chowdhury said according to seismic zoning map of Bangladesh, Dhaka comes under the highly earthquake prone zone 2. He said the consequences of earthquakes would be disastrous, as Dhaka's population is at least 10 million.
Mohammed Abu Sadeque, sub-divisional engineer of Public Works Department (PWD), clarified the reasons and effects of earthquake in his presentation. He quoted scientists anticipate a severe earthquake in Bangladesh.
"The Indo-Australian Tectonic Plate on which Bangladesh is situated is moving northward. However, the movement had stopped for the last hundred years storing 'strain energy' under the outer shell of the earth. This will cause a big earthquake in Bangladesh at any moment," he said.
Sadeque said there may be fissures on the ground and apart from complete damage, buildings may have settlements, tilts or cracks as effects of an earthquake. Fire is another problem that follows earthquakes.
"Dhaka is more likely to have fire hazards during earthquakes as its gas supply is piped," he said. 'Liquefaction' was highlighted in Sadeque's presentation as a major factor left by earthquake where the soil becomes soft like quicksand and unable to hold any structure. However, Dr Mehdi Ahmed Ansary, secretary general of BES, said in presentation that a comparatively less chance of 'Liquefaction' exists in Dhaka. "Only 10 per cent of ground in Dhaka may suffer from it as underground water level is gradually decreasing," he said.
The experts said proper earthquake proof construction is necessary for the safety of city dwellers. They said some construction firms try to convince people saying their buildings can bear an earthquake measured 7 or 8 on the Richter Scale.
Dr. Ansary added that an earthquake measuring 1 on Richter scale might get amplified into 2.5
because of the soil quality of a particular area.
He also said lack of maintenance of old buildings is posing a threat to city dwellers. "I have seen some buildings in old town, built on narrow columns with no foundation," said Dr. Ansary. "Imagine the plight of 20 lakh residents, if an earthquake takes place," he said.
Speakers said that in most cases an old building with no earthquake precaution could be made earthquake resistant by retrofitting. "It may cost 10 to 15 percent of the total construction cost of the building," said Abu Sadeque.
Experts said 90 percent of the city dwellers would be safe if buildings were constructed to meet the earthquake consequences. They stressed for a disaster management system for the other 10 percent. They added there should be stringent laws compelling builders to follow the earthquake code.
Syed Ashraful Alam, Md. Morshed and Mashiur R. Khandekar also made presentations. Tapan Kumar Das Gupta, DCC's chief town planner and Habibur Rahman, chief executive officer, also spoke.
There are some valid questions: Is Bangladesh vulnerable to earthquakes? Should we be concerned about an earthquake when occurrences of earthquake damages are not so significant? The country faces so many day-to-day problems related to environment, industrial pollution, traffic, water and power shortage, and annual calamities such as flood, drought, cyclone and tidal bore. Can we afford to ignore earthquake hazards?
Earthquakes are the detectable shaking of the earth's surface resulting from seismic waves generated by a sudden release of energy from inside the earth. Any landmass which has experienced natural ground shaking in the past is vulnerable to earthquake risk and thus liable to earthquake hazard. A severe earthquake can bring devastation to the economy of the country and we cannot ignore potential danger of earthquakes.
Bangladesh: A geological location for earthquakes
The geological structures in and around Bangladesh are capable of accumulating tectonic strain. These structures have released enough energy to produce destructive
shakes in the past.
Fortunately, the frequency of large earthquakes in and around the country is less than in other earthquake-prone regions of the world, though sometimes the lone national seismic observatory station at Chittagong measures a relatively high frequency of low magnitude shakes.
Bangladesh, along with its neighboring counties, shared the experience of extraordinary ground shaking due to an earthquake of magnitude 8.7 which is widely known as "The Great Indian Earthquake." The earthquake occurred due to a vertical displacement along the Dauki Fault located near the north-east international boundary between Bangladesh and India. The earthquake caused about 20m of pop-up of the Shillong Massive within a few seconds, and debris were blown even miles away from the epicenter area.
A similar strong and extraordinary earthquake of magnitude 7.5 occurred in Bhuj on January 26, 2001, damaging many urban areas of Gujarat and killing an estimated 25,000 people. Scientists consider these as rare earthquakes, but this type of earthquake could be extremely devastating in the peripheries of the Indian peninsula.
Bangladesh occupies a greater part of the Bengal basin. It is located in the eastern extremity of the peninsula and the Kutch basin in the western extremity is a mirror image of the Bengal basin. The regional geological structures from south to north at both the eastern and western extremities postulate a geometrical symmetry that would be receptive to similar tectonic behaviour in terms of stress distribution (except for some local differential characteristics). Considering such a geological setting, Bangladesh could be a receptive place for extraordinary earthquakes.
The rapidly growing urban centers increase the susceptibility of earthquake damage
Generally, unplanned and populous townships are always vulnerable to earthquake hazard or damages. Bangladesh is a densely populated country. At the beginning of the twentieth century there were only 48 urban centers in the country and at present there are 491 including the densely populated cities and growth centers. A rapid change in infrastructure development has resulted in significant changes in housing pattern and transportation, sewerage, water supply, waste disposal system and communication network. All development has taken place in a very short time. The planners and city managers could not keep pace for regulating the government's planned efforts in the face of such rapid development. The lack of planned development puts the cities and growth centers in a vulnerable situation for larger earthquake damages. The experts foresee the most deadly future for Dhaka mega-city in the event of an earthquake here.
Prediction of ground conditions
The geology of Bangladesh is complex due to the presence of about 100m to 1000m (30,000ft) of sedimentary deposits over the basement rock of Indian plate. More than 80% of the country is covered by soft sediments (soil) or holocene deposits with unpredictable changes in the upper 100m of deposits, having considerable variations in the constituent geological materials and geotechnical properties. The geological map of the country indicates that the upper 10m of sediments in about 60% of the land area is susceptible to liquefaction during earthquake, making the ground vulnerable to immediate shear failure.
More effort is needed for building up earthquake hazard awareness
As the frequency of earthquakes is low in Bangladesh, the people and government are not clearly aware of earthquake devastation and we can not afford any experiment with it. Building up of public awareness could be the first and essential step towards preparedness for reduction of earthquake damages. It is necessary to remember the alarming Dhaka Earthquake 2001, when strong tremors were felt in the city and many people rushed out of their homes and offices in panic. 100 prison inmates were hurt in a stampede at the Dhaka Central Jail.
What shall we do?
The country has had many damaging earthquakes in the past and is placed in a high seismic zone in the Global Seismic Hazard Map. We have not investigated the source structures, but due to its complex geological setting, Bangladesh is not capable of sustaining the strong shaking produced in the Himalaya and Meghalaya source area. Unfortunately, many of the infrastructures and buildings in Bangladesh may not meet BNBC standards and may be considered vulnerable from seismic safety viewpoint. Generally earthquake damages are irreparable. If we consider the potentiality of earthquake disaster, we may not be able to ignore this extraordinary geological hazard.
We are at the early stage of possible earthquake hazard assessment and cannot expect any overnight understanding of earthquake vulnerability of the country. But steps can be taken to reduce the losses and damages by implementation of Bangladesh National Building Code (BNBC) in the construction practice, identification of appropriate subsurface geology, determining the right type of architectural setting and engineering design of both foundation and superstructures, development of fire safety options, keeping open spaces for rescue operations, and other such measures.
At least we need an plan of action. There is an urgent need forreasonable seismic risk assessment of the country. It is a multidisciplinary task and includes technical training, institutional development, development of technical manuals, legal and enforcement aspects, and public awareness programmes.
Mir Fazlul Karim is Director, Geological Survey of Bangladesh.
Experts, stakeholders blame uncontrolled urbanisation, over population BSS, Dhaka
Experts and stakeholders at an workshop yesterday underscored the need for taking a long-term programme specially focusing in urban areas to face any natural calamities like earthquake.
Due to its geographic location, Bangladesh is vulnerable to earthquake and colossal damages of lives and properties may be occurred if the country faces an earthquake measuring five to six on the Richter scale, they said.
Uncontrolled urbanisation and over population put Bangladesh at high risk of earthquake , they added.
Minister for Disaster Management and Relief Chowdhury Kamal Ibne Yusuf attended the inaugural function organised by the ministry with the helpof European Mission Team at a city hotel as the chief guest.
E. Kentrschynskyj and Hans Rhein of EU Delegation in Bangladesh and Dr. John M Reynolds, team leader of Identification Mission spoke at the inaugurals session with AHM Shamsul Islam, Director General of Disaster Management Bureau (DMB) in the chair.
The minister said the government has undertaken various earthquake preparedness measures to mitigate the sufferings of the people and reduce loss of lives and properties. We are providing training to all concerned and creating awareness among the people to face such disaster, he added.
Citing expert opinion, he said Bangladesh is situated on the earthquake zone and any colossal damage may occurred if the country faces a moderate intensity earthquake. The country experienced at least 50 mild tremors last year with fear of another major earthquake, he added.
He said old and unplanned building construction in the capital city especially in the old part of Dhaka will lead damages of lives and properties in earthquake.
He said the government has taken a Comprehensive Disaster Management Policy (CDMP) for earthquake preparedness and mitigation. He sought cooperation from the development partners specially the European Commission (EU) to provide all out support in this regard.
A total of 40 representatives from the government organizations including Army, Navy, Air force, BDR, Fire Service, Civil Defence, Red Crescent Society, NGOs, and development partners are participating in the workshop.
Bangladesh runs high risk of quake, tsunami Experts tell roundtable Staff Correspondent
Bangladesh is running a high risk of earthquake and tsunami, but it has little preparation to combat those natural calamities, said the experts at a roundtable yesterday. They said the recent earthquake in Pakistan and tsunami in the Western Bay of Bengal are the warnings for Bangladesh.
The roundtable was organised by Volunteers Against Disaster (VAD) in association with the Disaster Research Training Management Centre of Dhaka University (DU) at the auditorium of geography and environment department.
The speakers said there are a few geological faults that can cause strong earthquakes in the country. One of them is Dauki fault at the bordering area of Sylhet-Meghalaya and the other one is Sitakunda-Teknaf fault at Chittagong coastal area.
There are many seismic faults in the plains around Dhaka and Chittagong Hill Tracts, which can cause earthquakes, said Geology Prof Syed Humayun Aktar.
"No earthquakes occurred in these faults for many years, which means huge strength has gathered underground that could cause serious earthquakes in Bangladesh and its neighbouring areas any time," he said.
Humayun Aktar said there is a long 600 kilometer seismic gap (that indicates possibility of
earthquake) stretching from the Andaman Islands of the Bay of Bengal to Teknaf where there is no record of earthquake.
"This is a great threat which could cause a strong earthquake measuring 8 in Richter Scale in Bangladesh, and turn into tsunami if the earthquake occurs under the Bay of Bengal,"
he warned.
Humayun Aktar said such tsunamis will directly hit Orissa of India, West Bengal and the total coastal belt of Bangladesh.
"As our coastal belt is only 750 km away from Teknaf-Andaman seismic gap, it will take only one and a half hours to destroy coastal localities," he added.
Humayun Aktar said if earthquakes with a magnitude of 7 occur in Bangladesh or in Meghalaya, Assam, Monipur, and Mijoram of India and at the bordering area of Myanmar, those will cause huge loss of life and property in the country.
Mir Fazlul Karim, director of Geological Survey of Bangladesh, said, “The 200 km long continental shelf is susceptible to earthquakes and landslides or slump failures along the margins. These locations are extremely potential for generation of local tsunamis, which are more destructive than the regional tsunamis."
He suggested development of a rapid seismic observatory system including hydro-acoustic sensors, sea height buoys and modern tide gauges as an integral part of early warning system for tsunami.
Md Abu Sadek, director general of Disaster Management Bureau, said the Building Code, now being reviewed, should incorporate the issue of earthquake as well as its strict implementation.
"We spend huge money for post-disaster management, but I think a portion of it should be spent on researches," he added.
Dr Ashraf Mahmud Dewan, assistant professor of geography and environment science department of DU, suggested that all organisations concerned have to share earthquake and tsunami-related information and create mass awareness among the people.
Dean of Science Faculty Prof RIM Aminur Rashid, Prof Abdur Rab, Prof Hafiza Khatun, Prof Nurul Islam Nazem, Prof Aftab Alam Khan, Deputy Director of Meteorological Department Arjumand Habib and Dr Aslam Alam of Comprehensive Disaster Management Programme of
Ministry of Food and Disaster Management also spoke at the roundtable moderated by Prof Jamal Khan.
Earthquake: Prediction and measures-M Muminullah
Face of the earth is changing through geological processes, sea floor spreading and plate tectonics. Earthquake is the outcome of such geological processes. Study of world wide frequency suggests that the more severe an earthquake, the less it occurs. A catastrophic earthquake with a magnitude more than 8.0 on Richter scale usually occurs once in every 5-10 years; disastrous on local scale with magnitude 6.2-6.9 about 100 or more in a year, and moderate (magnitude 4.3-4.8) more or less 5000 per year. Earthquake with magnitude less than 3.4 recorded only by seismograph, the annual number of such tremor is about 800,000.
So far at least 12 large-to-great earthquakes occurred in and around Bangladesh. In this context the people, government policy-makers as well as professional community
viz. engineers, architects, seismic geologists, planners etc may consider recurrence interval for
hazard avoidance through structural design and by proper land-use.
The Calcutta Earthquake of October 1, 1737 recorded a death toll of 300,000. This is the third most disastrous quake in this region which occurred during the last 800 years in terms of loss of life ( the highest deaths estimated 820,000 in 1556 at Shen-shu, China and the next
700,000 in 1976 at T'ang-shan, China).
The Assam Earthquake of June 12,1897 is one of the 10-graetest quakes occurred with a magnitude of 8.7 on the Richter scale and an intensity of VII on the Modified Mercalli Scale that caused a damage to the tune of US $25 million. The Bihar-Nepal Earthquake of January 15, 1934 recorded magnitude 8.1 and an Intensity X with a damage to the tune of US $ 25 million and estimated death toll of about 10,000.
The Chittagong Earthquake of April 2, 1762 recorded an Intensity of VIII on the Modified Mercalli Scale and a damage of US $5m. The Bengal Earthquake, Manikganj of July 14, 1885 recorded a considerable damage.
The Srimangal Earthquake of July 8,1918 occurred with magnitude 7.6 and recorded damage of more than US $1.0m.
Realising the earthquake hazards and its impact on national economy, Geological Survey of Bangladesh (GSB) took initiative in 1988 for a geological investigation on earthquakes and the potential hazards of their recurrence. In April 1989 Dr Darell G Herd of US Geological Survey along with representatives of GSB carried out a geological investigation to determine the tectonic origin of the Assam Earthquake of June 12, 1897 on the Dauki fault. A project titled "Detailed geological mapping for coal and other mineral exploration and Neotectonic study related to natural hazards" was initiated also for identification of major geological features for Earthquake Hazard Reduction Programme. Provision to install micro-seismic equipment was kept to collect seismic data of even smaller than magnitude 3.4 for neotectonic study.
A network of modern, wide frequency ,digital seismographic stations at Sylhet, Cox's Bazar ( alternately Chittagong), Mongla (alternately Khulna) and Rangpur would provide an accurate location (within several kilometers) for most earthquake events including even of smaller magnitude of 2 to 3 for preparation of micro-seismic map of Bangladesh.
During the 1897 quake, an area of more than 300,000 square km covering Bangladesh, India, Bhutan and western Mynmar was severely shaken. The fault origin of the 1897 Assam Earthquake may have originated on the Dauki fault running east-west along India (Assam)-Bangladesh (greater Mymensingh and Sylhet) border. Several other potential areas of geological features and elements are Dhaka-Srimangal lineament, the Tista lineament, the Atrai lineament, the Brahmaputra-Jamuna lineament, the Bogra fault(?), the Mymensingh lineament , the Tangail scarp, the Chittagong fault identified from interpretation of satellite imagery by GSB. Neotectonic study on such potential areas may be carried out to collect data on paleoseismology for Earthquake Risk Assessment Map by identifying active faults, fault scarps by detailed trench investigations, searching river banks, stream channels, irrigation ditches and excavations in flood plain materials for geological evidence of multiple liquefaction events and sand blows.
With such realisation on one hand and observation of the rapid growth of high-rise building and population, industrial establishments and commercial activities on the other, in the capital city Dhaka and the port city Chittagong, a report entitled, "Natural Hazards in Bangladesh:
Earthquakes" was prepared following the Chittagong earthquake of November 21, 1997 for awareness of the policymakers as well as the professional community. Considering the nature and extent of the earthquakes' threat or their recurrence, a strict compliance of the existing Building Code (which is not in force in Bangladesh) was suggested to build suitable engineered structures to minimise hazards.
The Chittagong Earthquake of July 27, 2003 occurred with a magnitude of 5.6 on Richter scale. From press repots, we observed that a crack was developed in Borkal area that called for detailed geological study, the nature and extent, slip rate and identification of earthquake features like sand boils, liquefaction, landslides etc. The 10-km crack is the rupture length of the fault segment produced by the Borkal Earthquake. This is a closely mimicked surface feature of the 1983 Borah Peak, Idaho, Earthquake (OJT 1989 under the supervision of Anthony J. Crone, USGS, Denver). Tremors in Chittagong and a small-scale tsunami (a long ocean wave produced by movement of sea floor following an earthquake) in Andaman sea on August 11, 2003 reveal the evidences of sea floor spreading and plate tectonic activated in the region.
Frequency, the nature and extent of the past earthquakes and recurrence of its behaviour suggest that a big earthquake event in Bangladesh may cause worst catastrophy, potentially more severe than that of the Calcutta Earthquake of October 1, 1737 when about 300,000 lost their life.
Earthquake is inevitable in the regions of seismic belt, but modern experiences with earthquakes in populated areas like the cities reveal the fact that properly designed engineered structures and constructed facilities can withstand even large earthquakes. So ensuring that appropriate engineering design and material standards keeping pace with sensible use of land and event prediction can thus serve effectively in reducing the loss of life and property in the event of a big earthquake.
( M. Muminullah is retired Director of Geological Survey of Bangladesh)
Potential earthquake threat and our coping strategies ( Dr M Shahidul Islam)
Although earthquake in Bangladesh has not yet been recognised as a case of serious natural disaster, but recent occurrences and assumptions have already generated a potential threat. The incidents of recent repeated earthquakes on 27 July in Chittagong have raised a great concern among the people of the country, particularly among those around Chittagong
region.
What is an earthquake?
It is a shock or a series of shocks on the earth surface resulted from release of pressure due to sudden movement of crystal rocks along active fault lines or plate boundaries of the earth surface or in areas of volcanic activities. Some parts of the world are earthquake prone more than others, although such event may happen at any place, any time and that of any magnitude. Japan, the Philippines, Southeast Asia and North America are particularly vulnerable to earthquake.
Geographically Bangladesh is located close to the boundary of two active plates: the Indian plate in the west and the Eurasian plate in the east and north. As a result the country is always under a potential threat of earthquake of any magnitude at any time, which might cause catastrophic devastation in less than a minute. In the seismic zoning map of Bangladesh, Chittagong region has been shown under Zone II with basic seismic coefficient of 0.05, but recent repeated jerk around this region indicate the possibilities of potential threat of even much higher intensity than projected.
A total of about six lackh incidents of quakes of different magnitudes occur annually throughout the world of which that of magnitudes 6-7, 7-8 and above 8 are 120, 18 andm1, respectively. The records in Bangladesh during the last 175 years shows total number of 25, 18 and 4 incidents of earthquakes having intensity more than 6, 7 and 8 on Richter scale, respectively. Among such incidents Bengal Eq of 14 July 1885 (R-7), Great Indian Eq of 12 June
1897 (R-8.7), Srimangal Eq of 8 July 1918 (7.6) and Assam Eq of 15 August 1950 (R-8.5) are well known. However, people's awareness regarding earthquakes in Bangladesh began to generate after the tragic death of Sadia (a little girl) in a quake of only R-5.6 magnitude on 21 November, 1997. Moreover, the incidents of repeated shocks between 22 July and 2 August, 1999 at Moheskhali and the damages to lives and properties could draw the attention of the nation considerably. Since then earthquake in Bangladesh has been considered as a potential natural killer to human lives. The last major earthquake in Bangladesh occurred about 30 years back. Statistically the threat of such a high magnitude tremor has the highest possibly to happen at any time, which might cause devastations particularly in Dhaka and Chittagong cities.
The occurrence of earthquakes is part of the natural process in the earth's geophysical system. Under the present stage of scientific development it is not possible to stop such natural events, and even if it was possible to do so, we should not intervene such internal system of the earth. However, understanding the characteristics of internal geophysical process of the earth and possibility of its forecasting can reduce the casualties from such incident considerably. Developed countries are doing continuous research in this field. Rather it is better to accommodate this event and develop technology to live with such incident, as we are living with cyclones, storm surges and floods. However, locating the epicenters and monitoring the characteristics of each shock may improve our understanding considerably and lead us to develop some preventive measure to live with earthquakes. It is thus immediate necessity to upgrade the existing earthquake measurement station at Ambagan in Chittagong and complete the two other proposed stations at Dinajpur and Sylhet.
Bangladesh has improved tremendously to mitigate and manage many of its natural disasters, although the mitigation strategies regarding earthquake has remained
nearly in its infant stage. At this stage the country does not need to take any radical measures to mitigate the earthquake incident, rather the concept of earthquake mitigation and management issues can be incorporated within the existing disaster management programme of the government, ranging from National Disaster Management Council to Union Disaster Management Committee. Proper training to voluntary organisations and NGOs, and procurement of instruments required for rescue operation must get top priority in the management agenda. Moreover, motivation programme and increasing of people's awareness can reduce the casualties from any earthquake incident considerably.
It is not the earthquake rather it is the building that kills people. If the collapse of even a single building can become possible to stop, it can save many lives residing in that building. It is not possible to abandon all old buildings, under the potential threat of earthquake. However, it is quite possible that all newly constructed buildings and structures must be brought under strict building code that resists earthquake damage.
Bangladesh is possibly one of the countries most vulnerable to potential earthquake threat and damage. An earthquake of even medium magnitude on Richter scale can
produce a mass graveyard in major cities of the country, particularly Dhaka and Chittagong, without any notice. Construction of new buildings strictly following building code or development of future controls on building construction are the activities which will be functional in future.
However, under the present stage of human occupancy, buildings, infrastructures and other physical structures of different areas of a city will not be equally vulnerable to any such
shock. Earthquake vulnerability of any place largely depends on its geology and topography, population density, building density and quality, and finally the coping strategy of its people and it shows clear spatial variations. It is thus necessary to identify the scale of such variations and take necessary measurements to cope with that.
Although the earthquake tremors cannot be stopped or reduced, the human casualties and loss of properties can be reduced with the help of an earthquake vulnerable assessment atlas. An earthquake atlas is the presentation of facts relating to earthquakes and the guideline for earthquake mitigation measurements at regional scale in the form of map, graphs, pictures and text. Such an atlas provides clear guidelines to post disaster rescue operation, regional scale mitigation strategies and stepwise disaster management activities. We do not have any such atlas neither at national level nor at regional level. However, it is the
timely demand to prepare an earthquake vulnerability assessment atlas of Bangladesh in general, and for the major cities in particular.
Large scale mitigation measurement needs huge initial investment; however, to save human lives and properties, we should not hesitate to do so. Particularly strict control of building codes, enforcement of laws and orders, and development of people awareness has
no alternatives.
However, some immediate measures are suggested below:
- Make an inventory of all old buildings which are vulnerable to earthquake, and either repair or evacuate occupants from those buildings.
- Make an inventory of houses, which are constructed at the foot of steep hillsides, particularly where hill slopes have been cut, even ten years back. Relocate those families to suitable places.
- Make earthquake vulnerability atlas of major cities, which will show in detail the list of vulnerable sites, their possible consequences and possible measurements of mitigation at different scales of earthquake events.
- Strict application of building codes for all newly constructed buildings, particularly all high rises buildings.
- Development of awareness programme to educate people regarding the causes and consequences of earthquakes. And also to disseminate knowledge to them regarding their responsibilities before, during and after the earthquake through seminar, symposium and workshop, and also through non-formal education by GO and NGOs.
During the 20s and 30s of the last century Japan lost 1.5 lackh human lives only in five earthquake incidents. But that society has faced this challenge successfully over the last 50 years. During the last 80s and 90s a total of 30 events hit the country causing loss of less than six thousand lives. Japan has not succeeded to stop earthquakes but has reduced the human casualties and loss of properties dramatically. At the present stage of our society and current level of development we may seem helpless but through our sincerity, honesty and commitment we may even do better than the Japanese society. We should therefore be optimistic and thus active.
(Dr M Shahidul Islam is Professor, Department of Geography and Environment ,Jagannath University Dhaka)
Bibliography :MH Ali and JR Choudhury, Assessment of seismic hazard in Bangladesh, Disaster Research Training and Management Centre, Dhaka University, Dhaka, 2001; JR Choudhury and MH Ali, Seismic Zoning of Bangladesh, paper presented in the Seminar on Recent Development Earthquake Disaster Mitigation, Organised by IEB and TAEE, Dhaka, 1994; KM Hossain,Tectonic significance and earthquake occurrences in Bangladesh, 7th GeologicalConference, Bangladesh Geological Society, 1989.
How prepared are we for an earthquake?
Interview with Director of Disaster Preparedness Centre
Muhammad Saidur Rahman is Director of Bangladesh Disaster Preparedness Centre, which has been working since 1991 in the field of capacity buildingof institutions, government and non-government, engaged in disaster management. The organization basically does research, policy formulation, strategy formulation etc. At the moment, it is working on capacity building of government organisation in case an earthquake hits the country. Mr. Rahman is a former college teacher of chemistry. He has also served as the deputy secretary general of Bangladesh Red Cross (now Crescent) Society as well as the country director of Oxfam. The interview was taken by Kaushik Sankar Das.
Daily Star (DS): Bangladesh, used to be called a country of natural disasters thanks to regular floods, cyclones etc. is recently struck by a new disaster, earthquake, in the coastal area and the hill tracts of Chittagong though there has not been much damage. Could you tell us how vulnerable we actually are in terms of a severe earthquake in the country?
Saidur Rahman (SR): A world famous seismologist Professor Billham said in 2001 that in the Himalayan region, at least seven earthquakes of the strength 8.1 and above on the Richter scale are overdue. A team of experts led by him did a survey and they identified seven to eight risk prone countries and Bangladesh is obviously one of them because of its geographical location. Secondly a study by a UN sponsored programme called International Decade for Natural Disaster Reduction in the period from 1991 till 2000 surveyed at least 30 different cities. And the findings of the survey are very threatening to us. They are saying that the two most vulnerable cities to earthquake are Tehran and Dhaka. There were several factors to come to this conclusion. For example situation in an earthquake zone, physical infrastructure, socio-economic condition of the people living there and most importantly response management.
DS:But why Dhaka? It's not listed in the primary earthquake zone in the region.
SR: Because Dhaka got zero points in the main categories. Thickness of buildings, poor quality of construction, poor socio-economic condition of people and above all poor response management were the main negative factors for Dhaka when the survey was done in 1998. All these put together Dhaka was on the top along with Tehran as the most vulnerable
cities when it comes to earthquake in the world.
DS: Has the situation changed since then?
SR: Well, let me put it this way -- we are more aware of the risks now than ever before. And the serious earthquake in Bhuj in Gujarat was responsible for the renewed awareness. A lot of people working in this sector went there including myself. One thing that really struck me was
that those organisations or institutions, responsible to help or rescue after a disaster hits, get affected by the disaster themselves, then how the response management would be put into effect. For example, the hospital, the water supply system in Bhuj were completely destroyed.
DS: Do similar flaws exist in Dhaka as well?
SR: More than enough, in fact the situation is worse in some cases. The fire brigade headquarters is situated in old Dhaka, if an area like that with narrow lanes and a huge population, is effected then what kind of help can we expect. Also the way utility services like WASA, DESA, Titas Gas have their supplies in densely populated areas, it would be not just
difficult but impossible to some extent to response to a disaster similar to the one in Bhuj. It takes them fifteen days to fix only one burst gas pipeline. Need I say more?
My realisation after visiting Bhuj was that this is not like other disasters like flood and cyclone. The speed with which government and non-government organisations can respond in those situations, is not possible when it comes to earthquake. Because the first job in earthquake is to rescue trapped people from inside collapsed buildings. And who can do this job better than those with proper equipment and training. For that we can only rely on government institutions. On my return, my organisation and Oxfam jointly went to meet the Minister for Disaster Management and Relief and he immediately bought the idea. And for the first ever time, national sensitisation seminar was held in Dhaka in March last year where the responsibilities of various government institutions in times of an earthquake were identified. The heads of all organisations attended the seminar and interestingly, but not unexpectedly, it was revealed that none of these organisations had any contingency plan. It never crossed anyone's mind that an earthquake can hit anytime and create such a havoc for which an integrated management was essential.
DS: Why do you think the government failed to sit up and take note of the situations from the devastating earthquakes in Kobe and then in Gujarat, especially since Bangladesh has remained as an earthquake prone zone for a long time?
SR: I think the government's priority and orientation changed mainly after the devastation in Bhuj in Gujarat. After the seminar last year, the Ministry took a lot of initiatives. The first one was that the capacity of the organisations would be developed. Six meetings were held and they were attended not only by the heads of the seventeen organisations, but also the minister, the mayor of Dhaka and other officials. And the outcome of those meetings could be described as some success, if not more. I wouldn't say they are hundred percent capable as yet, but they are definitely more sensitised to a crisis than ever before. They are ready to do something at least if a disaster strikes.
Secondly, to do something, not just awareness, they need some specialised equipment too. The government has been arranging with our help to hold a mock demonstration in old Dhaka to show physically what should be done immediately when an earthquake strikes. Since Sylhet and Chittagong region are also very vulnerable to earthquake, similar initiatives have also been taken to train members of government organisations for immediate response to earthquakes.
We have to remember that basic responsibility to protect the life and property of people
lies with the government and the government has the capacity and
resources to do that.
There is a government standing order for disasters. It describes the responsibilities of all the government organsiations from the PM's office to local Union Parishad in times of disasters, but earthquake is not included in the order. It was written a long time ago and revised in 1995. At the moment we are working on how to include earthquake in that
standing order.
DS: If the organizations are more aware and capable of tackling a crisis of this nature, then why have there been reports of no government assistance after the recent tremors in Chittagong and Rangamati?
SR: I would take it as a positive thing, because at least as soon as the reports of tremors began to trickle in, all these organisations were on alert and they were also alerted by the deputy commissioners. Since the damage was not severe in Chittagong City, nothing was seen. But if it was, maybe we would have witnessed those in action.
DS: Let's take a hypothetical scenario. If a severe earthquake strikes
in Dhaka city with narrow lanes, badly planned housing estates etc, are these organisations well prepared to respond immediately to the crisis, for example rescuing trapped people from collapsed houses?
SR: In one word -- no. They are not well equipped, though they are more sensitized. But at the same time Bangladesh Army has a contingency plan, Bangladesh Fire Brigade and Civil Defence Directorate has a contingency plan, Titas Gas has a contingency plan, WASA has a plan but all these organisations do not have proper equipment. That's why the ministry has
requested for a list of equipment from them. I don't know whether enough funds would be granted to buy the equipment, but I hope the government will take some initiative to arrange the fund.
DS: Apart from lack of equipment, which are the other areas that could pose a serious threat to the rescue work?
SR: First of all, there are very few cities in the world like Dhaka that have developed in such an unplanned manner. Building codes are never followed here. Secondly, there are no specific projects or ideas to keep us safe from earthquakes. For example, projects aided by Japan have specified certain areas in densely populated cities like Tehran, Manila, Turkey where specific laws would have to be adhered to in case one wants to build a new house, vulnerable buildings have been identified etc. Here we all know that there are codes but they are hardly implemented.
DS: But are those organizations responsible for ensuring the rules included in the programme that the government has taken up?
SR: Of course, RAJUK is one of the seventeen organisations who are part of this process. The RAJUK chairman attended two meetings; the additional chief engineer attends all the meetings. They are planning ways to revise the building code and make it more effective for
implementation. Then there are practical problems like lack of open spaces in the city where the affected people can be taken after a tremor. We are hoping that after the sensitisation process, we would be able to make proper use of our limited resources in a planned manner. We can at least reduce the risk, if nothing more. Take for example an area like old Dhaka. Even if the government wants, it can't relocate the inhabitants somewhere else, but the government can identify the empty spaces and playing fields that still exists there and make proper use of them. In a poor country like Nepal, the government decided to retrofit some schools, it means the buildings have been made earthquake proof by spending a little extra. Even the carpenters and masons are being trained. Here forget them, even the architects are not fully aware of the risks. So it's a long way to go.
What I want to say is that it's not the resources, it's the will that is required. And the ministry has shown a lot of interests in doing something constructive. We along with Oxfam are working very closely with the ministry and we have realised that not the non-governmental organisations', the roles of the government organisations are of utmost importance.
DS: What other measures have been taken to aware people about the risks and the things to do after a tremor?
SR: The ministry has prepared one hundred thousand brochures sponsored by UNICEF, two 90 seconds long short films funded by Oxfam have been made -- one addressing the common people on what they could do and the other aiming at the responsible organistations on what could be done by them. Apart from these, leaflets are being published for distribution in educational institutions. And the effort is on. I am very optimist by the level of seriousness shown by the government. But I agree that it will take time to achieve what we have set out to do.
Kaushik Sankar Das is an Assistant Editor of The Daily Star.
