Earthquakes

They tend to happen where plates collide or slide past each other. The colliding or sliding plates cause such a great compression below the surface that rocks bend and then crack suddenly. When this happens, shock waves spread out from the focus. This is the place where the cracks occur. The shock waves may cause the Earth's surface to tremble or 'quake' for several seconds. The earthquake is usually strongest at the epicentre, which is the surface area directly above the focus. Buildings may sway and eventually collapse if the force is strong enough.

tend to = regularly or frequently behave in a particular way collide =hit by accident when moving focus = the point of origin of an earthquake sway = move or cause to move slowly or rhythmically backwards and forwards or from side to side collapse = suddenly fall down