Point of origin of an earthquake or the point below a nuclear explosion or meteor air burst
A hypocenter or hypocentre (from Ancient Greek ὑπόκεντρον (hupókentron) 'below the center'), also called ground zero or surface zero, is the point on the Earth's surface directly below a nuclear explosion, meteor air burst, or other mid-air explosion. In seismology, the hypocenter of an earthquake is its point of origin below ground; a synonym is the focus of an earthquake. Generally, the terms ground zero and surface zero are also used in relation to epidemics, and other disasters to mark the point of the most severe damage or destruction.
https://en.wikipedia.org/wiki/Hypocenter