Importance Of Seismology

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INTRODUCTION Geophysical surveys have been used to identify the internal structure of the earth. Seismology is important for the study of the earth's interior because their resolving power is superior to that of other geophysical methods. This is because it provides depth, P-wave and S-wave propagation and velocities which are the basis for models for physical and chemical properties of each layer within the earth. (Stein, 2009) From geophysical surveys it has been found out that there are compositionally and seismically different layers within the earth. These are the solid outer layer called the crust which extends to about 40km below continents and to about 6km below oceans, the upper part of the mantle below the crust, the asthenosphere…show more content…
This includes the reflection, refraction and VSP methods that provide seismically defined layers of the earth. Work by seismologists in the first few decades of the twenty first century greatly refined the image of the earth's interior. Seismic waves, the vibrations generated during earthquakes, travel through the earth at 4-13km/s. The speed of these waves depends on properties such as density, compressibility, exposure to shearing of the material through which they are travelling and acoustic properties of the medium. When waves pass from one material to the other their velocities change depending on compositional changes and phase changes, dividing the earth into seismic discontinuities. Seismic discontinuities divide the mantle into three parts, the upper, lower mantle and the transition zone. Beneath ocean basins, the interval between100-200km has anomalously low seismic velocities; that is known as the LVZ. The slowness of seismic waves in this region are due to partial melting. 2-4% of the rock occurs as magma in thin films along surfaces or in small pores within grains. (Watts,…show more content…
The doming action leads to the formation of faults in the earth's crust and eventually rifting. The hot magma from the asthenosphere will rise through the faults forming volcanoes. There are two types of rifts namely passive and active rifts. Active rift are associated with upwelling asthenosphere, early uplift, abundant volcanic rocks. The uplift extends for 100s of km beyond the rift faults. Thinning of the lithosphere is spread over a wide area. Examples of active rifts include oceanic ridges, East African Rift System, aulacogens and back-arc
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