The important factors are:
Only outer crust is solidified to form the thin land layer. The radius of the earth is about 6000 km.Out of this, only 50 km is solid. So, in a radius of 6000 km, 50 km is < 1%.It is something like a balloon filled with water! But it is not bursting because, no one is hitting it!
Arrangements of layers
Outer layer is solid, next is liquid having molten rocks. Innermost layer is believed to be semi solid due to high pressure.
Rupture and re formations
Earth is still a dynamic system inside, with rupturing and re formation due to flowing of molten rock. This is also one of the reasons for Earthquakes.
There are divisions in the earth’s crust. It is not a single piece. So, these are called as Tectonic plates.These plates are moving against each other in some order. Whole of Himalayan Mountains are due to these movement. This is the most important reason for earthquake.
One of the important things is to know the history of quakes of a particular region. This will largely help in prediction.
Quake zone and data
There are zones in the world near the edges of tectonic plates which are prone to large and frequent earth quakes. Large data over a range of 10 years is to be collected for each zones for study.
Understanding the data
This is the trickiest part of all. Many times some intuitive talent is required to get a relationship and trend to match the huge data.
All the possible curve fittings of graphs and possible relations of the data are to be analyzed in detail to take a step in prediction
Knowing local factors
Local factors like mountains, buildings, rivers, lakes seas, volcanoes and underground faults will all affect the quake. Hence a good knowledge is required about these things
Extrapolation and prediction.
The graphs are to be extrapolated to get the prediction.
Preditions are difficult because there are many complicated variables and hidden local structuere of the earth.