Are we prepared for earthquakes in Sylhet?
A number of minor earthquakes occurred in the Sylhet region between 29 and 30 May 2021. Two earthquakes were also noticed on June 7, 2021 with some structural damage. The majority of seismic events with magnitudes were 2-3.4. Most earthquakes are detected by the Indian Seismological Society using its seismic system around Sylhet (Silchar, Shillong, Tura, Agartola, etc.). Only one seismic event (wave front only) was felt by the seismic station of the Bangladesh Meteorological Office on 29 May without sensing its magnitude and epicentre.
However, some news media are quoting chaotic headings of experts like "The tremors in Sylhet have been different. Due to the land plate the area is on, there will be a big earthquake there soon. So, we have to prepare the locals in Sylhet before the quake hits".
Media comments are partial and spreading misleading information without scientific evidence. Bangladeshis have a simple belief and confidence in the press with no justification. The latest news on social media and in the press is confusing and leading to panic - a situation that is intrinsically undesirable.
The Sylhet region is situated within an active tectonic frame with a deformed structure (like folds). Based on a seismic zoning map, we live in Sylhet in the susceptible seismic zone (red zone). The Dauki fault is one of the main faults that could generate an average earthquake a few dozen miles from Sylhet City. Apart from Dauki's fault, we also have the fault of Sylhet who produced a greater earthquake in 1918 (Srimangal earthquake). However, we could not estimate the most probable earthquakes in Bangladesh because the existing or blind fault zones are not well defined.
We need to know things for defining a large earthquake such as- a) length of fault zones (km), b) sliding angle + length of sliding surface (km), c) probable displacement (km), and d) recurring period (years). We do not know some of the parameters well. It is the matter of hope that some seismic stations and GPS were installed by different organizations recently. Wish that, we will able to define all parameters of fault planes in details.
We cannot undo events brought about by gas field activities. Gas field operations in the Sylhet area may be caused locally by smaller earthquakes. On the other hand it could be produced on fault plans. I do not think we should comment on this without proper investigation.
It is obvious that we are at risk of earthquakes and that smaller earthquakes damage our properties. Two buildings were inclined and cracks were observed in some structures, including the construction of Raja GC Secondary School. The experience of the engineers has shown that at least 30% of the buildings in the city of Sylhet are at risk while most of the buildings were not built according to the proper code. Some experts in the field have observed earthquakes of greater magnitude (7-8 Mw). Now, my questions are: a) To what extent are we prepared for future larger quakes? b) Can our constructions tolerate a larger earthquake? and (c) How can we be safe during and after an quake?
However, different kinds of preparation are available before, during and after an earthquake.
Preparations before an earthquake happens:
1. Practice general techniques such as Drop, Cover and Hold On with family members.
2. Establish a contingency plan: Create a family emergency communication plan that involves out-of-state contact. Plan where you will meet when you are apart. Prepare a supply kit with sufficient food and water for several days, a flashlight, a fire extinguisher and a whistle.
* Include non-perishable foods, cleaning supplies, and water for several days, in case services are cut off in your area. After an earthquake, you may not have access to these supplies for days or even weeks.
* Being prepared allows you to avoid unnecessary excursions and to address minor medical issues at home, alleviating the burden on urgent care centers and hospitals.
2. Keep in mind that not everyone can afford to fill up on basic necessities. For those who can afford it, making essential purchases and slowly stocking up supplies ahead will allow longer periods between shopping trips. This helps protect those who are unable to get the basics before the pandemic and have to shop more often.
3. Protect your home: Secure heavy objects in your home like libraries, fridges, TVs and hanging objects on walls. Store heavy, break-resistant items on low shelves. Consider making improvements to your building to deal with structural problems that could cause your building to collapse in an earthquake.
If an earthquake happens, protect yourself right away:
1. If you are in a car, pull over and stop. Set your parking brake.
2. If you are in bed, turn face down and cover your head and neck with a pillow.
3. If you are outdoors, stay outdoors away from buildings.
4. If you are inside, stay and do not run outside and avoid doorways.
After an earthquake, there can be serious hazards such as damage to the building, leaking gas and water lines, or downed power lines.
1. Expect aftershocks to follow the main shock of an earthquake. Be ready to Drop, Cover, and Hold On if you feel an aftershock.
2. If you are in a damaged building, go outside and quickly move away from the building. Do not enter damaged buildings.
3. If you are trapped, send a text or bang on a pipe or wall. Cover your mouth with your shirt for protection and instead of shouting, use a whistle.
4. You should avoid contact with floodwaters as they can contain chemicals, sewage, and debris.
5. Check yourself to see if you are hurt and help others if you have training.
6. If you are sick or injured and need medical attention, contact hospital for instructions. If you are experiencing a medical emergency, call emergency number.
The earthquake and the impact are not well known by the general population because we have not experienced dangerous events like floods and cyclones in recent decades. We have almost no preparation for an earthquake, no matter how average. However, we should prepare for the next earthquake, which occurred a hundred years ago. Another thing is that geology is ignored by the decision-maker while it has a huge role for any developmental activity. Geological feasibility work is carried out worldwide for all types of construction work. It's unfortunate that our geologists are always ignored by the respective authorities.
We are also unaware of our natural calamities. We have few plans for ensuring people's safety, including a better way of life. We're all busy playing self-serving games. Doing business with very simple and loyal Bangladeshi people using natural dangers is common. Now we are busy with earthquake, a couple of days ago we were with cyclones. Every year we have massive flooding, river erosion, landslides, logging in cities, and so on. However, we do not have a comprehensive management plan. We are sensitive, but we do not have much to think of.Based on present circumstances, the following suggestion can be implemented-
* Awareness raising
* Be prepared for EQ rescue operations
* There is a need for a dense seismic network in the country for earthquake records
* Buildings, bridges, tunnels etc. should construct in accordance with the codes
* A few EQ lessons should be included in the secondary education system
* Need for greater participation of geologists in all construction and development activities
Md Shofiqul Islam, PhD is a visiting Research Scientist, Lamont Doherty
Earth Observatory, Columbia
University, NY, USA and a Professor Department of Petroleum and Mining Engineering, Shahjalal University
of Science and Technology