Kazi Liakat Hossain :
Frequent tremors have resulted in grave concern among the general masses, especially those residing in Dhaka as they are believed to signal the possibility of a great earthquake. Experts believe that, big earthquakes follow the cyclic order. No big quake has jolted this region for the last 112 years. Earthquakes pose a great threat for the buildings of Dhaka, Chittagong and Sylhet. As two consecutive tremors hit Nepal leaving massive death in this year, earthquake experts here apprehend that an unprecedented human disaster may occur in Dhaka city and elsewhere in Bangladesh in case of heavy tremor as Bangladesh is situated in a high risk zone.
According to the experts, a powerful earthquake needs at least 100-150 years to be originated for a particular region and in that sense it is overdue for Bangladesh and parts of Assam, as 112 years have passed by since a heavy tremor from Dawki Fault hit the region. So, Bangladesh is highly vulnerable to a powerful earthquake, they said. Prof. Ansary, a prominent expert in this line has said – Bangladesh was earthquake prone as it lies along the border of Eastern and Indo-Australian plates, where tremors occur at regular intervals. In this region earthquake may take place in a cyclic order of hundred years. He further said, the great Indian earthquake of 1897 was more likely to be repeated every hundred years. Among the seven severe earthquakes of the Himalayan range, last one occurred in 1950. Some say that, in Cyclic order of hundred year’s earthquake in this region may not be true. But some opined that it might happen in cyclic order.
We know that the tremor measuring around5.00 on the Richter scale that jolted the Modhupur faults in 1885, another strong earthquake measuring 6.00 that rocked Moheskhali in 1999 and another rocked Rangamati in 2003 which was 5.69 on the Richter scale. In 1997, above 6.00 points tremor took place on May, 8 in Sylhet and destroying some buildings. On Nov. 21 in the same year, another tremor of 5.09 hit Chittagong and 5.69 tremor jolted Manikgonj on Dec.19,2001. In Dec. 2001, the entire North Bengal region including Dhaka- was rocked by moderate tremor which cracks in some of buildings in the capital city.
On September 21,2009 on the day of Eid-ul-Fitar, people of Dhaka as well as many districts of the country experienced moderate to strong earthquake measuring to 5.4 on the Richter scale that jolted the Bhutan-China border,462 Km north and north-east and the Myanmar region,552 Km north-east respectively from the Dhaka met office. Again on Sept. 10-11, 2010- a moderate tremor rocked Dhaka, Narayangonj measuring 4.5 on the Richter scale. Its epicenter was Chandpur district, Upazila north Matlab. At the time of massive disaster in Nepal of this year, several tremors-mild to strong measuring to 6.00 and up hit Bangladesh. In the month of June, July, August, September, October 2016 Bangladesh experienced small to moderate tremor. A Fatal earthquake that jolted recently caused a serious damage to lives property. It is apprehended that the frequent mild to moderate jolts signal a catastrophe which may claim thousands of lives and damage properties within a few seconds. The experts further warned that high rise buildings constructed after filling various water bodies like canals, ditches and low-lying areas were most vulnerable.
Ruling out the possibility of occurring a 7.8 magnitude tremor, one that hit in Nepal, in Bangladesh earthquake expert prof. Jamilur Reza Chowdhury said recently, a 7 magnitude earthquake may originate from Madhupur and Dawki faults. He said if an 8-9 magnitude of earthquake originates from Dawki fault, Dhaka will face an’ intensity of 7 on the Richter scale that may destroy a huge number of buildings leave nearly 1 lakh people dead. The Madhupur fault located near Dhaka city is very active to generate a moderate to heavy earthquake. A big earthquake originated from the fault in 1885, 127 years ago. Now energy is being accumulation of seismic energy beneath the city. ‘With the passage of time, the present plate boundary is shifting from east to West Jamuna-Meghna river basin, which put Dhaka at risk of tremor’-he said.
Showing earthquake data, Prof. Humayun said a 4.5 magnitude tremor originated from Madhupur fault beneath the Buriganga River on Dec. 19 in 2001 while two more small quakes occurred from the fault in 2008, epicenters- Manikganj and Mymensingh. ‘That means Madhupur is an active fault. And when energy accumulation will reach a critical level, the energy will be released leading to a devastating quake from the fault that will critically affect Dhaka city’, said Dr Humayun, a professor of the Geology Department of Dhaka university. Although Dhaka is less vulnerable to tremor than Sylhet and Chittagong, it will experience massive damage due to soft formation of soil if one moderate quake hit the capital city, Prof. Jamilur Reza said.
‘Unplanned urbanization and construction of buildings filling up the low-lying areas and wetlands intensify the earthquake-risk for Dhaka city, ‘he added. According to Rajuk, Seismic expert’s opinioned that, a huge number of structures and buildings of Bangladesh, Including Dhaka Chittagong and Sylhet, will completely be destroyed if a moderate tremor hit the country. A study conducted by the Comprehensive Disaster Management Programme(CDMP) of the Bangladesh government in 2010 revealed the doomsday scenario of tremor’s vulnerability and its possible consequences.
The study showed that some 78,323 buildings will be destroyed completely if a 6- magnitude earthquake shakes Dhaka, causing havoc throughout the densely populated capital city. In case of a 7.5-magnitude earthquake from Madhupur Fault, some 72,316 buildings will be partially destroyed. If an 8.5- magnitude tremor from the plate boundary of Fault-2 hits the region, Some 238,164 buildings will be destroyed completely across the country. There will be an economic loss of about US$1.1 billion resulting from only structural damage in case of a 7.5- magnitude from the Madhupur Fault. Economic loss due to damage of structures will be US $650 million and US $1.07 billion respectively in case of an 8- magnitude earthquake from the plate boundary-2 and in case of a 6- magnitude earthquake from under Dhaka city, the study says. A 7.5-magnitude earthquake from the Madhupur Fault Economic loss due to damage of structures will be US$ 650 million and US&1.07 billion respectively in case of an 8-magnitude earthquake from the plate boundary -2 and in case of a 6-magnitude earthquake from under Dhaka city, the study says.
A 7.5-magnitude earthquake from the Madhupur Fault will generate a total of 30 million tones of debris, killing some 131,029 people instantly and injuring 32,948 others. According to the study, at least 10 major hospitals, 90 schools in the capital will be destroyed completely and another 241 hospitals and clinics,30 police stations and four fire stations partially in case of a 7.5- magnitude quake. The geological survey of India complied the first seismic zone of the sub-continent in 1963. Three zones were indicated in the maps, liable to severe damage, liable to moderate damage and liable to slight damage. This qualitative map was based mainly on records of tremor occurrence in the past. A major part of Bangladesh-in the north, north-east and south-east, was shown under ‘liable to severe damage’. In the event of recurrence of earthquakes similar to the 1897, a large number of buildings in Dhaka would collapse.
The prime requirement is the availability of equipments for carrying out search and rescue operations. Unfortunately, no such equipment is available in Dhaka city. For example, in the aftermath of the Jagannath hall auditorium roof collapse in 1985, it was found that the fire service and Civil defense authorities did not have single vehicle equipped to rescue the people trapped under math the roof trusses. Preparedness can reduce fear enxiety and losses that accompany disasters. Communities, families and individuals should know that to do in the event of a quake. The basic principles of survival in a tremor drop down, or take cover under strong structure such as a table or bed and hld on to something until the quake passes or try to go to open field quickly if there is any nearby.
When tremor takes place, a big power or energy gets free, the weight of the power or energy is measured by a scale. In 1935, Charies Richer invented this scale for measuring the power of earthquake. ‘Richter scale’ has been named after the name of the inventor scientist Charies Richter. In 1960, Chile experienced severest earthquake on the Richter scale 9.50. No tremor has been occurred on the Richter scale 10.00 yet in the world. May Almighty Allah relieve us from this devastating tremor.
