Is a mega earthquake imminent in Bangladesh?

Recently, some research was shared across print and electronic media where it was predicted that a 9.0 magnitude mega-earthquake will hit the central-eastern part of Bangladesh, especially in and around Dhaka city. This prediction not only puts the 140 million residents of the capital city at risk, but also raises immense concerns as to the fate of the costly public and private civil structures, industries, flyovers, and other necessary public amenities. In fact, the prediction is even more ominous because most of the recent infrastructure was designed and built to withstand 7-magnitude earthquakes that may hit this region. Understandably, the prediction of a 9.0 magnitude earthquake is frightening news to the government, since all the mega-projects such as power stations, multi-storied garments manufacturing factories, airports, sea ports, mega-bridges, dams, satellite towns, economic zones, etc in Bangladesh were undertaken to withstand a 7.0 magnitude earthquake, not 9.0. This is a grave concern for the investors in both the public and private sectors. The outcome of the research and several interviews of the authors shared across social media have become viral, causing quite a bit of anxiety among the residents. One of the authors even suggested a complete abandonment of the city. Thus, in this pretext, it is necessary to examine the outcome of the scientific study which was published recently in the reputed Nature Geoscience journal. The research paper postulated the existence of a plate boundary in and around Bangladesh. This is an extremely odd finding since other maps created by scientists from a number of reputed institutions and organisations across the world (GSB, USGS, GSI, DU, RU, etc) do not show any kind of plate boundaries (birthplaces of all earthquakes) or deformation zones in and around Bangladesh. As a matter of fact, the aforementioned maps, known as the geological and tectonic maps of Bangladesh, were prepared by many renowned local and foreign geo-scientists in the past on the basis of geo-physical, borehole, and outcrop data. What is more baffling is that the researchers took the liberty of shifting the meeting place of plate boundaries several hundred kilometres west of the actual place known to the scientists of the world. They did it on the basis of ground movement which was estimated by several GPSs. The shifting of subduction zone is also up for debate, as it is an established fact that the plate in the location of interest is moving side by side and not subducting (the downward movement of the edge of a plate beneath another plate). If the plates are not subducting, then there is an extremely low probability of earthquake, which contradicts the published research. Additionally, the westward movement of the plates was ascertained using only the GPS data interpretation. But predicting an earthquake of any intensity not only requires long-term GPS data observation, but also requires detailed geophysical survey (beyond basement), borehole (for 3-D basin modeling), and outcrop data interpretation along with historical records of earthquake occurrences in that region. Thus, to bring everything into context, the published research in Nature Geoscience clashes with the existing knowledge regarding the geological and tectonic maps of Bangladesh, such as: a) the existence of subduction or deformation zone which was never mentioned or determined before (therefore not yet established); b) whether that locked up deformation zone can produce an earthquake of that magnitude; c) will the mega-earthquake have the intensity to shake Dhaka along with the Bengal Basin as predicted; and d) whether the casualties of life and properties will be as much as predicted or later opined by authors. Government agencies dealing with earth science, especially geology (as earthquake is a geological phenomenon), need to address this issue by undertaking projects to conduct detailed studies urgently.Detailed geophysical surveys of several tens of square kilometres followed by drill holes that were done for oil and gas in the past will help immensely in finding subsurface plate boundaries or deformation zones. A 3-D model of the Bengal Basin needs to be prepared from different deep drill-hole data of the country to fully understand the severity of earthquakes in different parts of the basin.

 Read More: http://www.dhakatribune.com/opinion/op-ed/2016/08/04/on-solid-ground/

Posted by admin on Aug 4 2016. Filed under Bangladesh Exclusive. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry