what are the main cause of earthquake?

Answer 1

1.earth plates shifting
2.the fragile and thin parts of earth
3.volcano

Answer 2

An Earthquake is a sudden tremor or movement of the earth's crust, which originates naturally at or below the surface. The word natural is important here, since it excludes shock waves caused by French nuclear tests, man made explosions and landslides caused by building work.
There are two main causes of earthquakes.
Firstly, they can be linked to explosive volcanic eruptions; they are in fact very common in areas of volcanic activity where they either proceed or accompany eruptions.
Secondly, they can be triggered by Tectonic activity associated with plate margins and faults. The majority of earthquakes world wide are of this type.
Terminology
An earthquake can be likened to the effect observed when a stone is thrown into water. After the stone hits the water a series of concentric waves will move outwards from the center. The same events occur in an earthquake. There is a sudden movement within the crust or mantle, and concentric shock waves move out from that point. Geologists and Geographers call the origin of the earthquake the focus. Since this is often deep below the surface and difficult to map, the location of the earthquake is often referred to as the point on the Earth surface directly above the focus. This point is called the epicentre.
The strength, or magnitude, of the shockwaves determines the extent of the damage caused. Two main scales exist for defining the strength, the Mercalli Scale and the Richter Scale.
Earthquakes are three dimensional events, the waves move outwards from the focus, but can travel in both the horizontal and vertical plains. This produces three different types of waves which have their own distinct characteristics and can only move through certain layers within the Earth.

Answer 3

All kinds of things can cause earthquakes:

1. volcanic eruptions
2. meteor impacts
3. underground explosions (an underground nuclear test, for example)
4. collapsing structures (such as a collapsing mine)

But the majority of naturally-occurring earthquakes are caused by movements of the earth's plates.

We only hear about earthquakes in the news every once in a while, but they are actually an everyday occurrence on our planet. According to the United States Geological Survey, more than three million earthquakes occur every year. That's about 8,000 a day, or one every 11 seconds!

The vast majority of these 3 million quakes are extremely weak. The law of probability also causes a good number of stronger quakes to happen in uninhabited places where no one feels them. It is the big quakes that occur in highly populated areas that get our attention.

Answer 4

The earths crust is made up of Tectonic plates and for the most part they don't move. At times from either the inner core of the earth building up heat from magma or pressure from gases it causes the plates to shift which then causes an earthquake. Depending on the amount of pressure or explosion size determines how high on the Richter Scale it ends up being. This site can explain it very well. I even ended up getting a refresher and a whole new interest in that stuff again.

Good luck and I hope this helps. :-)

Answer 5

Earthquakes are caused by a sudden release of stored energy inside the Earth's crust. This energy causes seismic waves, which can lead to the effects of Earthquakes of which I am sure you are familiar.

Answer 6

movement of underground rock ( a small percentage are caused by movement of magma )

this occurs in 'fault' areas ( weak points in the crust ) not just where plates meet

Answer 7

a shift in the earths plates