This is simply a retelling of stories from those who lived through the raids. People who have been shook by them.
It’s typical hyperbole that should tell how extreme the bombings were. To those who experienced them. Like earthquakes they shook the ground and its echoes lasted for days. Bombs of course have an immediate reaction and the resulting blast will dissipate within a moment or two ( I suspect some nuclear bomb shockwaves last longer or rather go further and echo back more powerfully than substantially smaller bombs ) and not perpetuate for days. However the image of it clearly does and did.
The image the character should have should be one of absolute destruction.