In Papua New Guinea, there was a recent 7.5 magnitude and it was caused by a subduction of one of the tectonic plates. This recent event destroyed homes and triggered landslides. Right now, New Zealand, Papua New Guinea are both included in the ring of fire.
It is called "The Pacific Ring of Fire," The reason being is because it is the most likely place where their are lots of earthquakes and volcanoes that happens. But when it comes to earthquakes, they release something called a seismic wave that looks like rippling water. The first two waves are called P-wave and S-wave.
A P-wave travels faster than the S-wave and the P-wave stretches the earth forwards and backwards as it spreads outwards. S-waves however, is the opposite of P-waves and they move slower than the usual speed. The S-wave arrives second and they travel in a up and down kind of motion. A magnitude means how big the earthquake is and it's also measured from 1 to 10.
Most people get confused with the epicentre, it is part of the earthquake that is placed on the ground and it is also directly above the slip. This means it is where the earthquake slip, happened to the ground. A seismelogists is a scientists who studies earthquakes, their movement and how big their magnitude is.
The only time that earthquakes occur, is when both the tectonic plates underneath the crust slips past each other very quickly. Also, earthquakes under the ocean cause tsunami's. This is what I've learnt about earthquakes and the events that causes and what the aftershock is, once an earthquake or tsunami has passed through a city, country or even a village.