Topic                               : Basic Exploration of Seismology
Speaker                           : Mr. Irwan, M.Sc.
Date                                 : March, 07th 2013
Place                                : Physics Computation Laboratory
Amount of Participants      : 26
Resume                            :

                   The interior structure of the earth is layered inspherical shells like an egg. The first layer called crust, the crust ranges from 5–70 km in depth and is the outermost layer. Second layer called mantle, earth's mantle extends to a depth of 2,890 km, making it the thickest layer of Earth. And the last layer of the earth is core, the core is divided into two parts, a solid inner core with a radius of ~1,220 km and a liquid outer core extending beyond it to a radius of ~3,400 km.
Structure of the Earth

                 An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Seismic waves are waves of energy that travel through the Earth's layers, and are a result of an earthquake, explosion, or a volcano that imparts low-frequency acoustic energy. An earthquake's hypocenter is the position where the strain energy stored in the rock is first released, marking the point where the fault begins to rupture. This occurs at the focal depth below the epicenter.The epicenter is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates.

Seismic Wave

                 There are many types of seismic waves, S waves and P waves. Primary waves (P-waves) are compressional waves that are longitudinal in nature. P waves are pressure waves that travel faster than other waves through the earth to arrive at seismograph stations first hence the name "Primary".  These waves can travel through any type of material, including fluids, and can travel at nearly twice the speed of S waves. Secondary waves (S-waves) are shear waves that are transverse in nature. These waves arrive at seismograph stations after the faster moving P waves during an earthquake and displace the ground perpendicular to the direction of propagation. S waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses.

P waves and S waves
                 Deformation is a change in the shape or size of a rocks due to an applied force (stress and strain). Elasticity is a physical property of materials which return to their original shape after they are deformed. There are basic concept for seismology, Young’s Modulus, Poison Ratio, Bulk Modulus, Shear Modulus, and Lamb’s Constants.

Source : Mr. Irwan, M.Sc - Corner of SEG SC UB at March, 07th 2013

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