History of Earthquake Incidents in Bangladesh

HISTORY OF EARTHQUAKE INCIDENTS IN AND AROUND BANGLADESH

Accurate historical information on earthquakes is very important in evaluating the seismicity of Bangladesh in close coincidences with the geotectonic elements. Information on earthquakes in and around Bangladesh is available for the last 250 years. The earthquake record suggests that since 1900 more than 100 moderate to large earthquakes occurred in Bangladesh, out of which more than 65 events occurred after 1960. This brings to light an increased frequency of earthquakes in the last 30 years. This increase in earthquake activity is an indication of fresh tectonic activity or propagation of fractures from the adjacent seismic zones. Before the coming of the Europeans, there was no definite record of earthquakes. Following is a chronology of important earthquakes from 1548.

Chronology (1548 – 2003)                                                                    

1548	The first recorded earthquake was a terrible one. Sylhet and Chittagong were violently shaken; the earth opened in many places and threw up water and mud of a Sulphurous smell.
1642	More severe damage occurred in Sylhet district. Buildings were cracked but there was no loss of life.
1663	Severe earthquake in assam, which continued for half an hour. Sylhet district was not free from its shock.
1762	The great earthquake of April 2, which raised the coast of Foul island by 2.74m and the northwest coast of Chedua island by 6.71m above sea level and also caused a permanent submergence of 155.40 sq km near Chittagong. The earthquake proved very violent in Dhaka and along the eastern bank of the meghna as far as Chittagong. In Dhaka 500 persons lost their lives, the rivers and jheels were agitated and raised high above their usual levels and when they receded their banks were strewn with dead fish. A large river dried up, a tract of land sank and 200 people with all their cattle were lost. Two volcanoes were said to have opened in the Sitakunda hills.
1775	Severe earthquake in Dhaka around April 10, but no loss of life.
1812	Severe earthquake in many places of Bangladesh around May 11. The earthquake proved violent in Sylhet
1865	Terrible shock was felt, during the second earthquake occurred in the winter of 1865, although no serious damage occurred.
1869	Known as Cachar Earthquake. Severely felt in Sylhet but no loss of life. The steeple of the church was shattered, the walls of the courthouse and the circuit bungalow cracked and in the eastern part of the district the banks of many rivers caved in.
1885	Known as the Bengal Earthquake. Occurred on 14 July with 7.0 magnitude and the epicenter was at Manikganj. This event was generally associated with the deep-seated Jamuna Fault.
1889	Occurred on 10 January with 7.5 magnitudes and the epicenter at Jaintia Hills. It affected Sylhet town and surrounding areas.
1897	Known as the Great India Earthquake with a magnitude of 8.7 and epicenter at Shillong Plateau. The great earthquake occurred on 12 June at 5.15 pm, caused serious damage to masonry buildings in Sylhet town where the death toll rose to 545. This was due to the collapse of the masonry buildings. The tremor was felt throughout Bengal, from the south Lushai Hills on the east to Shahbad on the west. In Mymensingh, many public buildings of the district town, including the Justice House, were wrecked and very few of the two-storied brick-built houses belonging to zamindars survived. Heavy damage was done to the bridges on the Dhaka-Mymensingh railway and traffic was suspended for about a fortnight. The river communication of the district was seriously affected (brahmaputra). Loss of life was not great, but loss of property was estimated at five million Rupees. Rajshahi suffered severe shocks, especially on the eastern side, and 15 persons died. In Dhaka damage to property was heavy. In Tippera masonry buildings and old temples suffered a lot and the total damage was estimated at Rs 9,000.
1897	Known as the Great India Earthquake with a magnitude of 8.7 and epicenter at Shillong Plateau. The great earthquake occurred on 12 June at 5.15 pm, caused serious damage to masonry buildings in Sylhet town where the death toll rose to 545. This was due to the collapse of the masonry buildings. The tremor was felt throughout Bengal, from the south Lushai Hills on the east to Shahbad on the west. In Mymensingh, many public buildings of the district town, including the Justice House, were wrecked and very few of the two-storied brick-built houses belonging to zamindars survived. Heavy damage was done to the bridges on the Dhaka-Mymensingh railway and traffic was suspended for about a fortnight. The river communication of the district was seriously affected (brahmaputra). Loss of life was not great, but loss of property was estimated at five million Rupees. Rajshahi suffered severe shocks, especially on the eastern side, and 15 persons died. In Dhaka damage to property was heavy. In Tippera masonry buildings and old temples suffered a lot and the total damage was estimated at Rs 9,000.
1918	Known as the Srimangal Earthquake. Occurred on 18 July with a magnitude of 7.6 and epicenter at Srimangal, Maulvi Bazar. Intense damage occurred in Srimangal, but in Dhaka only minor effects were observed.
1930	Known as the Dhubri Earthquake. Occurred on 3 July with a magnitude of 7.1 and the epicenter at Dhubri, Assam. The earthquake caused major damage in the eastern parts of Rangpur district.
1934	Known as the Bihar-Nepal Earthquake. Occurred on 15 January with a magnitude of 8.3 and the epicenter at Darbhanga of Bihar, India. The earthquake caused great damage in Bihar, Nepal and Uttar Pradesh but did not affect any part of Bangladesh.
	Another earthquake occurred on 3 July with a magnitude of 7.1 and the epicenter at Dhubri of Assam, India. The earthquake caused considerable damages in greater Rangpur district of Bangladesh.
1950	Known as the Assam Earthquake. Occurred on 15 August with a magnitude of 8.4 with the epicenter in Assam, India. The tremor was felt throughout Bangladesh but no damage was reported.
1997	Occurred on 22 November in Chittagong with a magnitude of 6.0. It caused minor damage around Chittagong town.
1999	Occurred on 22 July at Maheshkhali Island with the epicenter in the same place, a magnitude of 5.2. Severely felt around Maheshkhali island and the adjoining sea. Houses cracked and in some cases collapsed.
2003	Occurred on 27 July at Kolabunia union of Barkal upazila, Rangamati district with magnitude 5.1. The time was at 05:17:26.8 hours.

(Ali & Chowdhury, 2009)

STATUS OF EARTHQUAKES IN BANGLADESH

(Ali & Chowdhury, 2009)

Bangladesh is surrounded by the regions of high seismicity which include the Himalayan Arc and shillong plateau in the north, the Burmese Arc, Arakan Yoma anticlinorium in the east and complex Naga-Disang-Jaflong thrust zones in the northeast. It is also the site of the Dauki Fault system along with numerous subsurface active faults and a flexure zone called Hinge Zone. These weak regions are believed to provide the necessary zones for movements within the basin area. 

 

In the generalized tectonic map of Bangladesh the distribution of epicenters is found to be linear along the Dauki Fault system and random in other regions of Bangladesh. The investigation of the map demonstrates that the epicenters are lying in the weak zones comprising surface or subsurface faults. Most of the events are of moderate rank (magnitude 4-6) and lie at a shallow depth, which suggests that the recent movements occurred in the sediments overlying the basement rocks. In the northeastern region (surma basin), major events are controlled by the Dauki Fault system. The events located in and around the madhupur tract also indicate shallow displacement in the faults separating the block from the alluvium. 

 

The first seismic zoning map of the subcontinent was compiled by the Geological Survey of India in 1935. The Bangladesh Meteorological Department adopted a seismic zoning map in 1972. In 1977, the Government of Bangladesh constituted a Committee of Experts to examine the seismic problem and make appropriate recommendations. The Committee proposed a zoning map of Bangladesh in the same year. 

 

In the zoning map, Bangladesh has been divided into three generalized seismic zones: zone-I, zone-II and zone-III. Zone-I comprising the northern and eastern regions of Bangladesh with the presence of the Dauki Fault system of eastern Sylhet and the deep seated Sylhet Fault, and proximity to the highly disturbed southeastern Assam region with the Jaflong thrust, Naga thrust and Disang thrust, is a zone of high seismic risk with a basic seismic co-efficient of 0.08. Northern Bangladesh comprising greater Rangpur and Dinajpur districts is also a region of high seismicity because of the presence of the Jamuna Fault and the proximity to the active east-west running fault and the Main Boundary Fault to the north in India. The Chittagong-Tripura Folded Belt experiences frequent earthquakes, as just to its east is the Burmese Arc where a large number of shallow depth earthquakes originate. Zone-II comprising the central part of Bangladesh represents the regions of recent uplifted Pleistocene blocks of the Barind and Madhupur Tracts, and the western extension of the folded belt. The Zone-III comprising the southwestern part of Bangladesh is seismically quiet, with an estimated basic seismic co-efficient of 0.04.

EARTHQUAKE RISK IN BANGLADESH AND IN THE CAPITAL DHAKA

The present generation of people in Bangladesh hasn't witnessed any major earthquake. As a result the population has been generally complacent about the risk of earthquakes. During the last seven or eight years, the occurrence and damage caused by some earthquakes (magnitude between 4 and 6) inside the country or near the country's border, has raised the awareness among the general people and the government as well. The damage has been mainly restricted to rural areas or towns near the epicenter, but there have been some instances of damage in urban areas 50 to 100 km away. 

 

Dhaka, located in the central region of Bangladesh, could be affected by any of the four earthquake source zones, presented earlier. Another point of major concern is that there are active faults near the city also. This was realized during the 19 December 2001 magnitude 4+ Dhaka earthquake that caused panic among many city residents. The epicenter was very close to Dhaka city. Frightened people in several high rise buildings rushed down the stairs, as they felt considerable shaking in the upper floors. The location of a probable earthquake source so near Dhaka with the probable earthquake magnitude needs to be further investigated. 

 

The 1993 Bangladesh National Building Code provides guidelines for earthquake resistant design. The code provides a seismic zoning map which divides Bangladesh into three seismic zones: The north-northeast potion which includes Sylhet, Mymensingh, Bogra, Rangpur falls in the zone "liable to severe damage" (0.25g motion). The middle and southeast portion which includes Dinajpur, Sirajganj, Naogaon, Dhaka, Feni, and Chittagong fall in the zone “liable to moderate damage" (0.15g motion). The rest of the country in the south-west falls in the zone “liable to slight damage" (0.75g motion). 

 

All the above discussions were intended to show that we are, indeed, living with the possibility of a major earthquake affecting major cities of Bangladesh. This may occur at any time. Next we need to think about the extent of damage likely for such earthquakes.

The urban areas in Bangladesh have developed in a fast pace to accommodate the increasing population resulting in extensive construction of multi-storied buildings. In the absence of legal enforcement of the building code in the country and lack of earthquake awareness in the country, many multistoried buildings have been constructed without proper earthquake consideration. The various factors contributing to the earthquake risk in the urban and rural areas of Bangladesh may be summarized below:

- Absence of earthquake
- Awareness.
- High population density and construction lacking earthquake resistant design
- Absence of legal enforcement of building code and its seismic design provisions
- Poor quality of construction materials and improper construction method
- Economic limitations
- Possibility of fire outbreaks due to rupture of gas pipelines or electric short-circuit during an earthquake and inadequate fire fighting facilities
- Inadequate road width and space between buildings preventing rescue operations and fire-fighting vehicles to reach certain areas.
- Inadequate exit (at the same time) for the occupants of a building during an emergency.
- Lack of facilities (rescue equipment, trained staff, medical personnel, and medical facilities) and preparedness for emergency response and recovery operations following an earthquake.
- Lack of earthquake resistant design of life line facilities which include power plants, power stations, bridges, communication control stations, gas and water supply stations etc.

The buildings in Dhaka city may be broadly classified into two groups: unreinforced brick masonry (URM) buildings and reinforced concrete frame (RCF) buildings. URM buildings have been observed to behave poorly during earthquakes and they can be more dangerous if they are 4 or more stories high, or built on 5 inch walls, which is not uncommon in Dhaka. RCF construction can also pose equivalent danger if earthquake resistant design provisions are not followed; this has been amply demonstrated in recent earthquakes of Bhuj and Izmit. Economic reasons, lack of quality control in construction and use of poor quality of materials all contribute to the high vulnerability of buildings. A recent building survey, funded by Bangladesh Ministry of Science and Technology research grant, in parts of Sutrapur, Lalbagh and West Dhanmondi reveals concentration of multi-storied URM buildings in the older part of the city. While the percentage of URM buildings in Sutrapur area of the old city was found to be around 65%, the same in the relatively new West Dhanmondi was found to be around 42%. Using Chinese building damage data, the writer has estimated that an intensity VIII earthquake could result in complete or partial collapse of more than 5% and serious damage to around 15% buildings. Intensity VIII corresponds roughly to the ground motion of 0.15g assigned to Dhaka city in the Building Code. (Al-Hussaini) This is a preliminary rough estimate, more detailed survey and analysis is necessary for reliable damage and loss estimation. Foundation problems such as earthquake induced ground settlement, liquefaction of loose sandy deposits under water or amplification of ground motion in certain soft soil areas or filled up areas of the city may also substantially increase the damage of buildings. Local soil effects can thus lead to intensity greater than VIII in certain areas of the city causing more damage.

 

Impact of Earthquakes

Recent Japan Earthquake : moment Tsunami hits Miyako City
Impacts of earthquakes can be classified into various classes-

Ground rupture- It is the main result of an earthquake strike. Shaking of ground causes severe damage to the buildings or other structures on the ground including houses etc. Shaking of ground at a particular place depends upon the distance of that place from the epicenter. Severe shaking of ground causes destruction of all the buildings of a city and many people die by burring into the building materials. It can’t be avoided because earthquakes strike a place all of a sudden. So this shaking of ground compels construction engineering to develop buildings which are resistive to the strikes of earthquakes. The branch of engineering deals which deals with anti-earthquake construction is called Earthquake construction.

Landslides- Earthquakes causes instability of land results into landslides; this claims many lives at the effected zone.
Fire- Earthquake causes breaking of electrical power lines or gas supply lines which causes incidents of fires. Water lines also got ruptured and decreased pressure makes it impossible to control the spread of fire. In earthquake of San Francisco in 1906, more deaths happened because of fire as compared to earthquake itself.

Soil liquefaction- When severe shaking occur then soil or sand loses their strength for a temporary period and gets converted from solid to liquid. This liquefaction causes sinking of buildings, bridges etc.

Tsunami and floods- when epicenter of an earthquake is located near sea, then the traveling of seismic waves below the sea causes generation of Tsunami waves, which can travel at a speed of 600-800 kilometers per hour. For creation of Tsunami earthquakes are needed to be highly intensified. In general earthquakes having reading of less than 7.5 on the Richter scale are not able to generate Tsunami waves. But stronger earthquakes can are comfortable enough to create Tsunamis. Sometimes when earthquake triggered landslides fall into sea, it leads to the creation of Tsunami waves.                                                                                                            

See what happened in recent earthquake in JAPAN 

 

Predictions and Safety Measures

EARTHQUAKE: PREDICTION AND MEASURES

(Munimullah)

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 worldwide 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.

Realizing 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 geotectonic 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 geotectonic 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. Geotectonic study on such potential areas may be carried out to collect data on pale seismology 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 realization 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 minimize hazards.

The Chittagong Earthquake of July 27, 2003 occurred with a magnitude of 5.6 on Richter scale. From press reports, 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 behavior suggest that a big earthquake event in Bangladesh may cause worst catastrophe, potentially more severe than that of the Calcutta Earthquake of October 1, 1737 when about 300,000 lost their life.

POTENTIAL EARTHQUAKE THREAT AND OUR COPING STRATEGIES
 

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 organizations 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 most vulnerable countries 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 don’t 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:

1.                  Make an inventory of all old buildings which are vulnerable to earthquake, and either repair or evacuate occupants from those buildings.

2.                  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.

3.                  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.

4.                  Strict application of building codes for all newly constructed buildings, particularly all high-rise buildings.

5.                  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.

As Dr. M. Shahidul Islam, Professor of Department of Geography, University of Chittagong says –

“During the 20s and 30s of the last century Japan lost 1.5 lakh 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.”

EARTHQUAKE DISASTER MITIGATION

(Al-Hussaini)

Earthquakes cannot be prevented, but its damage can be reduced with suitable measures. While Bangladesh has achieved remarkable success in disaster management for frequently occurring hazards such as cyclone, tornado and floods, it is at an infant stage with regard to earthquakes. We have a long way to go, but at least in the past few years, some encouraging activities have started and are continuing with both individual and institutional efforts. The Government has also stressed the importance for developing a national earthquake management system and has taken steps in this regard.

The Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET) has been involved in earthquake engineering education, research and consultancy services for several years. The Department took the lead role in the preparation of the 1993 national building code which included a new seismic zoning map and earthquake resistant design provisions. The department proposed the formation of a national centre for earthquake engineering at BUET and subsequently got USAID funding for a link project with Virginia Tech, USA. BUET has also been largely involved in the formation of Bangladesh Earthquake Society (BES) in 2002. The first election of the executive body of BES was held in 2003. BES is a multi-disciplinary national professional society dedicated to the cause of preparing the nation to face the threat of possible earthquakes. The organization is expected to create a bridge linking different sections of the people, working together with the government, to achieve a common goal of reducing the earthquake risk. BES, in collaboration with the Ministry of Food, Disaster Management and Relief (MFDMR) and the Disaster Management Bureau (DMB) has already organized several seminars. Earthquake research centers or groups have been formed at several universities, what is needed next is recognition of these groups and collaboration among different groups and individuals. Modern digital seismic instruments, recently installed, are being operated by BUET and Dhaka University, with government and foreign funding. Non-governmental organizations and international organizations are also participating in this effort. BES is publishing a newsletter that gives information on recent activities, earthquake news and articles of interest. The society is also aiming to develop a website which would be an information resource for interested people. BES will also publish relevant manuals or books.

For earthquake disaster mitigation, both professional and government solution is needed. Professional solution will be provided by engineers, architects, planners, geologists on technical aspects and social scientists, non-governmental organizations and mass media on social aspects. In the professional solution, civil engineers have the leading role to play, since it is the collapse of civil engineering structures that result in earthquake disasters. For the estimation of probable ground motion, engineers and geologists should work together. Financial institutions, builders and industrialists would be required to support the professional solution. Government solution includes the involvement of the concerned ministries and government or semi-government agencies in implementing the professional solution through policy making and policy enforcement. It needs to be clearly determined who would have regulatory jurisdiction over what.

For earthquake disaster mitigation, the following measures should be given top priority:

1.                  Increase public awareness about earthquakes through mass media, education (at school), training, earthquake drills, publications etc.

2.                  Refined assessment of probable ground motion and identifying local soil effects

3.                  Reliable assessment of probable damage to buildings and other structures.

4.                  Updating of the building code

5.                  Legal enforcement of building code.

6.                  Building insurance to promote earthquake resistant construction.

7.                  Seismic strengthening of critical structures and facilities.

8.                  Developing laboratory and testing facilities for research.

9.                  Developing low-cost seismic strengthening techniques so that individual house owners are encouraged to adopt them.

10.             Training of engineers, planners, architects and construction workers.

11.             Automatic safety shutdown system for gas and electricity during a major earthquake

12.             Developing facilities for post earthquake rescue and recovery.

13.             Urban (including transport) planning of the city to mitigate earthquake effects.

14.             Implementation of national earthquake disaster management plan involving various professionals, officials and volunteers. 

 

New Technique to Monitor Earthquakes

(Blog: Discovery News, 2009)

Scientists have come up with a new technique to monitor movements beneath the earth's surface which could help us discover more about earthquakes, it has been revealed. A research team, led by Andrew Curtis, professor of Mathematical Geosciences at the University of Edinburgh, simulated the motion of one earthquake at the location of another to learn more about underground movements using computers. The team collected the information of underground movements with the help of seismometers. The technique, which was developed during the course of a year, could also increase the number of locations that could be used to detect seismic activity, according to the study published in the journal Nature Geosciences. Speaking on the new method, Prof Curtis said: "This turns the way we listen to seismic movements on its head. By using earthquakes themselves as virtual microphones that record the sound of the earth's internal movements, we can listen to the earth's stretching and cracking from directly within its most interesting dynamic places.

"The key to the new method is to understand the theory of sound waves. It's more about back-projection - which is when we use a computer to send the sound wave of an earthquake down to the epicenter of another earthquake in order to measure the movements more precisely."

The team included a scientist from Utrecht University in the Netherlands and a scientist with the British Geological Survey.                                             

 

Earthquake Safety Measures and Tips

New Construction - Strengthening

Here are some useful tips for new construction and strengthening of existing buildings.

Buildings should be designed by a competent engineer following the 1993 Bangladesh National Building Code. Earthquake resistant design involves the use of steel which is a ductile material. It is not economically possible to design a building to resist the extreme earthquake forces without some damage. The building code allows some damage at preferred locations but prevents building collapse and provides safety to life and property. Steel gives the building necessary properties to resist collapse if they are provided at the correct locations of the structure. Structural elements that provide the earthquake resistance include concrete or masonry shear walls, concrete frame, braced frame, rigid floor system and proper connections between them. Proper detailing of the steel reinforcements at critical locations of the building structure is of great significance. ACI (American Concrete Institute) code gives seismic design detailing requirements for reinforced concrete buildings. Other standard building codes such as IBC2000 may also be consulted.

Strengthening of non-engineered buildings can be done following the IAEE (International Association for Earthquake Engineering) manual on Guidelines for Earthquake Resistant Non-Engineered Construction.

Certain building types are likely to be more susceptible to serious damage or collapse and thus require structural assessment for earthquakes by a competent engineer. Such buildings if not properly designed may need special strengthening measures.

Some typical examples are given below:
- Old URM buildings with cracks in walls and roofs on timber beams.
- URM buildings on 5 walls.
- Multi-storied URM buildings with discontinuous lintel.
- Multi-storied RCF building with open parking space on ground floor. Soft-story action or weak column-strong beam action should be prevented.
- Multistoried buildings with large cantilever projections.
- Multi-storied buildings of irregular (unsymmetrical) shape or having setbacks.
- Buildings having mass eccentricity.

- Buildings with flat plates.
- Buildings having elevated water tanks or swimming pool on roof top.
- Adjacent multi-storied buildings with little gap, hence possibility of pounding.
- Slender high rise buildings.
- Buildings on soft soil (fill material).

When an Earthquake occurs:
During an earthquake, people are injured or killed by falling plaster, collapsing walls, roofs or falling of heavy objects. Collapsing buildings and vibrations can cause short circuits and electric fires. Lighted gas or stoves may also cause fires. This creates panic and confusion.

Do's and Don'ts during an Earthquake:

If you are indoors:
- Stay calm.
- If you are in the ground floor and you can get out very quickly (5-10 secs), rush outside to an open space away from buildings or electric posts. Usually earthquake shaking lasts less than a minute.
- If you do not have time to go outside, stay at selected places inside your buildings which are relatively stronger against earthquakes such as near strong columns or near closely spaced walls in both directions. Stay away from outer verandah, balconies, cantilever projections, outer walls, doors and windows.
- Get under a table or a sturdy cot so that you are not hurt by falling objects from above.
- Stay away from glass windows, almirahs, showcases, and mirrors etc.
- Stay away from falling plaster, bricks or stones.
- Do not rush towards broken or jammed doors or staircase.

If you are outdoors:
- Move to nearby open space.
- Keep away from tall chimneys, buildings, balconies and other projections.
- Be careful, hoardings or lamps in the street may fall on you.
Do's and Don'ts following an Earthquake:

- Switch off all electrical appliances such as refrigerator, TV.
- Turn off the gas.
- A battery operated radio will help you to get important messages.
- Wear shoes to protect your feet.
- Do not crowd around damaged areas or buildings.
- Keep the streets clear for emergency services.
- Do not waste water.
- Use first aid if someone is hurt. Do not move seriously hurt people. Wait for medical help to arrive.
- If possible, assist children, old and disabled persons and the sick.
- Be prepared for more shocks which always follow a major earthquake.

 

Conclusion

Earthquakes pose a gigantic threat to the economy and well being of this country. While thousands of buildings may collapse in the cities, serious casualties could be in tens of thousands. Seismic risks should be correctly assessed and subsequently mitigated to the extent feasible. A comprehensive and well-coordinated earthquake disaster mitigation plan for the urban as well as rural areas should be developed without further delay and implemented on a priority basis with available resources. Earthquake engineering research centers should be promoted to be focal points for providing expert technical guidance to the country for earthquake disaster mitigation. Such centers can also provide effective education and training of related professionals. Building codes need to be updated and improved. Effective interaction and dialogue between the technical professionals and the government authorities should be ensured. Success of earthquake disaster mitigation efforts will depend on the blending of technical and political solutions into best practices for the reduction of unacceptable risk and sustainable development. Priorities should be established for strengthening the most critical structures and lifeline facilities. The participation of various government, non-government and voluntary organizations, academic institutions, community leadership and media should be encouraged and integrated for maximum benefit.