📍 Seismic Network: Epicentre Location from S-P Times and the Error Ellipse (2D)

Map of a network of seismic stations that measure the delay between the P and S waves of an earthquake, turn each delay into a distance and find the epicentre where the circles meet, with wave fronts spreading out from the true source and a cloud of repeated locations with their error ellipse. Set the wave speeds, the pick error, the number and layout of the stations, the position and depth of the quake, and see the distance rule, the error ellipse and the Wadati diagram. The noise-free solution, the error ellipse, the scaling of the error and the Wadati slope are checked numerically, with four in-page numerical checks.