Question

How are earthquakes classified? Explain their causes.

Answer 1

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Earthquakes are classified on a no. Of basis. Of these the depth of focus, the cause of origin and intensity are important.

 

a) Depth of focus:

 

Three classes of earthquakes are recognized on this basis, shallow, intermediate and deep seated. In the shallow earthquakes the depth of focus lies anywhere up to 50 km below the surface. The intermediate earthquakes originate between 50 and 300 km depth below the surface.

 

 

b) Cause of origin:

 

i)       Tectonic earthquakes are originated due to relative movements of crystal block on faulting, commonly, earthquakes are of this type.

 

ii)  Non tectonic earthquakes: that owes their origin to causes distinctly different from faulting, such as earthquakes arising due to volcanic eruptions or landslides.

 

C) Intensity as basis:

 

Initially a scale of earthquakes intensity with ten divisions was given by Rossi and ferel. Which was based on the sensation of the people and the damage caused. However it was modified by Mercalli and later by wood and Neumann.

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