Ensure buildings are earthquake-resistant

THE EDITOR, Madam:

Newer, or older building? Does your building have serious cracks after the ‘deggeh deggeh’ 4.9-magnitude earthquake last Thursday evening? Likely, you have a ‘weak storey’ where there are lots of columns, lots of windows or a higher ceiling, compared to other floors and just a few walls as compared to other floors.

Years ago, Margaret Grandison, who was the head of the Earthquake Unit, told us (a group of JIE engineers) that based on our historical record, we should expect about a seven-magnitude earthquake. This would be in the same range as had occurred a few years ago in Haiti. Each time you go up one in magnitude, for example, from five to six, the energy of the earthquake goes up by a factor of 10. So, from five to seven the energy goes up by 10 times 10, or 100 times.

If your building is showing serious cracks after only a 4.9-magnitude quake, do you think it will survive 100 times the earthquake energy when the big one comes? Poor construction with porous bands of gravel in a column can also cause problems, even if there is the right amount of reinforcing steel bars are in it. Accept nothing but proper design and construction.

HOWARD CHIN

Member

Jamaica Institution

of Engineers