The mountainous regions of Central and Southern Asia are particularly prone to earthquakes because of the geologic forces that created and are still creating - the Himalayas.
"Plate tectonics" is the term geologists use to describe movement along the earth's crust. According to this theory, the entire outer shell of the earth is broken up into seven plates that skim over the liquid mantle below. When plates collide and pull apart, the force creates mountains, volcanoes, cracks in the ocean floor...and earthquakes.
The Indian Plate is moving north and colliding with the Eurasian Plate. As it moves, it is being pushed beneath the Eurasian Plate, and the steady upward thrust has created some of the highest mountain ranges in the world, including the Himalayan, the Karakoram, the Pamir, and the Hindu Kush. The Indian Plate only moves about 40 millimeters a year, but that is enough to create intense compression close. That compression causes the earth's crust to fracture, creating what is called a "fault".
When the blocks of crust on each side of the fault move, that is an earthquake.