fault line
Focus/Hypocenter
A fault line.
It causes and earthquake
The epicenter is the point where motion begins on a fault line in the event of an earthquake. This location is seen as the origin of the earthquake itself and can help determine how much damage has been done in different areas.
Rupture along a 40 km section of the San Andreas fault.
its directly below the epicenter
plates of the earth crash into each other along faults causing an earthquake
All of them. For example: the earthquake of 2010 in Chile happened along a convergent fault while the 2010 earthquake in Haiti happened along a transform fault. Source: I am just a genius...
bending of the rocks followed by slipping...
Earthquake foci can be used to mark the earths plate boundaries . The movement along the plate boundary causes the earthquake. Knowing where the foci is can help predict future earthquakes in that scientists can monitor the area for shifts in the plates.
The largest earthquake of the 20th Century happened along the coast of South America. It is known as the Great Chilean Earthquake.
Oh, how I do hope you are below an 8th grade level to be asking this question. The cause of an earthquake is the plates and faults scraping and moving along eachother, the movement of the plates causes the earthquake. That is how they are involved.