Epicenters of earthquakes and eccentricity of an orbit.?

Question

im taking the earth science practical tommorrow and i need about epicenters and ellipses. What is the "p wave travel time" in an earthquake and how do u calculate it? What is the the time of origin of an earthquake and how do u calculate it?

And about eccentricity, the more closer the eccentricity to 1, the more oval the ellipse is? If u call the orbit of something to be eccenrtic it is ovalish rite?

Thanks in advance!

Answer 1

The arrival time of S wave minus P wave in seconds multiplied by 8 will give you the distance of focus  in K/M .Because the difference in speed between these two waves are 8 k/m per second.The ratio of the speed is 1.7 : 1.

The epicenter is an imaginary point just above focus point on the surface of the earth.The path of earth is elipse.But the Sun is not at correct middle point.