The source categorizes them separately and I followed that categorization. The deadliest earthquake was the 1976 Tanghan earthquake and it does mention that some coal mines flooded but doesn't say how many deaths this accounted for out of the total figure of 655,000. The 2011 Japan earthquake caused 19,759 deaths but also doesn't break down deaths due to flooding. I'm sure there's an overlap between them, but I don't have the data to show that it would make a big enough difference to change the all-time deadliest in each category.