Introduction to earthquake engineering complete notes ebook free download pdf
Long time ago, a large collection of material masses coalesced to form the Earth. Large amount of heat was generated by this fusion, and slowly as the Earth cooled down, the heavier and denser materials sank to the center and the lighter ones rose to the top. The differentiated Earth consists of the Inner Core(radius ~1290km), the Outer Core (thickness ~2200km), the Mantle(thickness ~2900km) and the Crust(thickness ~5 to 40km). Figure 1 shows these layers. The Inner Core is solid and consists of heavy metals (e.g.,nickel and iron), while the Crust consists of light materials (e.g.,basalts and granites). The Outer Core is liquid in form and the Mantle has the ability to flow. At the Core, the temperature is estimated to be ~2500°C, the pressure ~4 million atmospheres and density ~13.5 gm/cc; this is in contrast to ~25°C, 1 atmosphere and 1.5 gm/ccon the surface of the Earth.