Evidently you found your pants if you just had to change them. Also, I didn't know you had more than one pair of pants.
This was a headquarters building explosion, not a refinery.
It's in Mexico City and I was there not long after an earthquake there in downtown Mexico City and a building was collapsed. I was told it collapsed during the earthquake because part of its building materials was plastic foam instead of steel. After hearing that, I don't trust any building in Mexico City to stand up very long if there is any kind of outside stress.
IIRC, the earthquake was in 1985 and another problem (besides lousy construction) was the ground - not stable, but filled in old lakebed.