Md. Fakrul Islam Chowdhury writes for DOT :
Seismologists can guestimate the magnitude of an Earthquake from measuring how long an earthquake lasts. . Fifteen seconds Earthquakes hit more than 6.8 in Richter scale. A thirty-second earthquake generally has a magnitude in the mid-sevens. A minute-long quake is in the high sevens, a two-minute quake has entered the eights, and a three-minute quake is in the high eights. By four minutes, an earthquake has hit magnitude 9.0.
How much causality an earthquake would cause depends on the density of the population as well as the way the habitat/ City is built and structured though.
On May 22, 1960 in Chile on a fault that is almost 1,000 miles long, the largest earthquake ever was recorded. It was a magnitude 9.5 earthquake. It killed 1655 people, injured 3000 and displaced two million. It is estimated that US$550 million damage was caused by this earthquake.
An Earthquake of Magnitude about 8, In Shensi, China, on Jan. 23, 1556
Resulted in about 830,000 deaths.
In recent history an earthquake of Magnitude 9.1 caused 227,898 deaths in Sumatra, Indonesia, on Dec. 26, 2004.
Whereas the 1989 earthquake in Loma Prieta, California, took sixty-three human lives and caused six billion dollars’ worth of damage.
The key to limiting damages caused by an Earthquake is preparedness and disaster management.
It’s about time we start a conversation in the mainstream media that would effectively and engagingly help us think about the unthinkable–an idea of what wide-scale devastation by a Magnitude 8 or over earthquake might look like in a post-earthquake Dhaka and how, practically and psychologically, one might survive it.
In a 2016 study published in the journal Nature Geoscience, it was revealed that
Dhaka, one of the most densely populated cities in the world, with its 18 million inhabitants sits on top of a fault buried under thick sediments, which could trigger a massive earthquake.
If an earthquake between 8 and 9 to occur, Dhaka will be reduced to rubble and may become literally uninhabitable.
Currently, there is little or no awareness that power and gas connections must be turned off the moment an earthquake is sensed because fires from the damaged transmission lines will cause devastation beyond our imagination and jeopardize the rescue operations after an earthquake
In Dhaka only a portion of the buildings are built in accordance with the National Building Code. These buildings would be able to withstand earthquakes of the magnitude of seven on the Richter scale. Whatever happens when an earthquake of higher magnitude hits, is anybody’s guess.
A 2014 World Bank funded study based on a probable model of a 7.5-magnitude earthquake along the Madhupur fault line estimated that around 88,000 buildings would be extensively damaged.The study further showed that the monetary damage that would result in Dhaka if such an earthquake to hit the city would be around $5.6billion
Prof Mehedi Ahmed Ansary of the civil engineering department in Bangladesh University of Engineering and Technology (BUET), in an interview with Dhaka Tribune said,
“In addition to faulty building construction practices, the rapid use of the city’s floodplain will play a role in possible building collapse and subsequent human causalities if an earthquake of 7.5 magnitude hits Dhaka.”
It’s about time we start formulating and implementing awareness programs and also start building Earthquake shelters on a priority basis.
Disaster preparedness and disaster management squads of volunteers should immediately be formed and training should be provided to them.
Our civil and military forces should have special training to combat this kind of disasters.
But first thing first.
We can no longer afford to bury our face under the sand.
The conversation on “The Big One” begins here and now.
The writer is Consulting Editor, AmaderNotunShomoy