Chapter1:The generation of earthquakes and the damage they cause

1 The generation of earthquakes

(1)How earthquakes are generated

(i)The internal structure of the Earth The earth, a globe with a radius of 6,370km, is composed of the internal core, the external core, the mantle and the ｣縒nst.

Figure 1: The inside of the Earth

a. The crust

The outermost part of the Earth, the crust has a depth of from 30 to 75km over the land surface, and from 5 to 7km over the water surface. It has a density of from 2.5 to 2.8g/cm3 and is formed by eruptions from below, their transformations or accumulations

b. The mantle

Located under the crust, up to 2,900km from the surface, the mantle is formed of alkaline rock with a density of from 3.3 to 5.6g/cm3. Even though a solid, the temperature becomes hotter and hotter, and over a very long span mantle flow can be observed.

c. The core

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