I believe you are what are the causes and sequence of events leading to earthquakes.
Earthquake refer to shaking of ground under influence of disturbances that take place in sections of large chunks of earths outer crusts. A severe earth quake releases energy that may be of the order of 10,000 time the energy released by the first atom bomb.
Earthquakes are caused by collision between large chunks of earth's called tectonic plates. The total outer crust of the earth is divided in 30 such plates. These plates are supported by molten rocks underneath. The plates are moving constantly but very slowly along the surface of the molten rocks beneath them. During the course of their movement there is a relative movement between these plates which cause them to slide past each other, and in the process some parts of edges of different plates come closer or move away from each other. The portions of edges also slide past each other in close contact.
These relative movement between plates create great stresses in rocks near the edges of the plate, causing large chunks of rocks to bend. When the stress becomes too much the rocks break and readjust in new positions, causing shaking of the earth in that position. This place where the initial disturbance is caused is called epicenter of the earth quake. The shock waves created at the epicenter, called seismic waves, spread out radially and causes earthquake wherever it travels. However as the seismic waves spread out radially they become weaker and the intensity of earthquake reduces with the distance from the epicenter and finally subside completely.
There are many good web sites with reliable information about earthquakes. Here are some suggestions of reliable sources for you to review. Check out the information provided by the University of HI at http://www.soest.hawaii.edu/GG/ASK/earthquakes.html You will find a short explanation about what causes earthquakes in a emergency preparedness brochure published by the California Governor's Office of Emergency Services at http://www.oes.ca.gov/Operational/OESHome.nsf/PDF/EQ%2014%20tips/$file/eq_causes.pdf