The definition of a deep red alert is a hazard to the entire city, but the range between the upper and lower limits is actually quite vast.
Blown out of proportion, a Chromatic Spider with meme interference ability could barely be counted for a deep red alert (the spider horde consumes a hundred people a day, over thirty thousand a year),
a nuclear explosion over a city can also qualify as a deep red alert.
（Modern nuclear weapons systems, compared to their yield, pay more attention to increasing the weapon's survivability and accuracy. Taking the U.S. military's currently active 450-kiloton TNT equivalent W88 nuclear warhead as an example, its thermal radiation burn radius is only 8.62 km. It would take a dozen, several dozen, or even a hundred of them to devastate a modern large city）
To trigger seismic waves of that magnitude, you'd need at least the energy level of several nuclear bombs.
"Confirmed, it's nothing serious."
