Bangladesh vulnerable to earthquake

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 help of 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)