Using seismic wave produce by earthquake to
- 1. USING SEISMIC WAVE PRODUCE BY EARTHQUAKE TO STUDY THE EARTH INTERIOR ONUORA, CHIDI FRIDAY ESUT/2014/147961 DEPARTMENT OF GEOLOGY AND MINING FACULTY OF APPLIED NATURAL SCIENCE ENUGU STATE UNIVERSITY OF SCIENCE AND TECHNOLOGY FEBRUARY, 2018
- 2. PRESENTATION OUTLINE INTRODUCTION DEFINATION OF SEISMIC WAVE TYPE OF SEISMIC WAVE HISTORY OF SEISMIC APPLICATION DETERMINATION OF EARTH COMPOSITION USING SEISMIC WAVE EVIDENCE THAT SATISFIES THE SEISMIC FINDING IN EARTH INTERIOR CONCLUSION
- 3. INTRODUCTION Earthquake occur when energy stored in elastically strained rock is suddenly released. This release of energy causes intense ground shaking in area near the source of the earthquake and send wave of energy called seismic wave throughout the earth. This wave grouped into body wave and surface wave propagate throughout and outside the earth interior. seismic wave travel at different velocity through layers of the earth interior, Variations in seismic wave velocity are used to infer the properties of Earth’s interior.
- 4. DEFINITION OF SEISMIC WAVE Seismic wave are elastic energy released in form of vibration from the focus of an earthquake and travel out throughout the earth. Type of seismic wave Surface wave: they spread out from the epicenter and travel along paths nearly parallel to the surface of the earth. They are of two type ;Love wave Rayleigh wave. Body wave: are seismic wave that emanate from the focus and travel in all direction through the body of the earth. They are grouped into two primary wave and secondary wave.
- 5. Figure 1. Earthquakes and Seismic Waves (source: Dunkin Park, 2008) BODY WAVE P - waves - are Primary waves. They travel with a velocity that depends on the elastic properties of the rock through which they travel. Where; Vp is the velocity of the P-wave, K is the incompressibility of the material, μ is the rigidity of the material, and ρ is the density of the material. S- Waves - Secondary waves, also called shear waves. They travel with a velocity that depends only on the rigidity and density of the material through which they travel:
- 6. HISTORY OF SEISMIC APPLICATION Mohorovicic Discontinuity • The imaginary line of discontinuity that separate the brittle crust of the earth from the mantle is Mohorovicic discontinuity or moho for short. • Boundary between the crust and the mantle in the earth. • Depth where seismic wave change velocity and there is also change in chemical composition. Figure 2. Analysis of body wave arrival times at a global network of seismographic observatories (source: D.P. McKenzie, 2007 )
- 7. GUTENBERG DISCONTINUITY • Boundary between the lower mantle and outer core • Depth where seismic wave change velocity and direction. primary waves slowed down dramatically and secondary waves stopped entirely. Figure 3. seismic wave velocity of earth interior. (source: Stephan Kusek, 2003)
- 8. DETERMINATION OF EARTH COMPOSITION USING SEISMIC WAVE A Modern Image of Earth’s Layers Figure 4. The velocity-versus-depth profile of the whole Earth (source: Mihai Andrei,2015)
- 9. TABLE OF DEPTHS, DENSITIES, AND COMPOSITION OF EARTH INTERIOR Table of depths, densities, and composition. Anderson, D.L., 1989. Thickness (km) Density(g/cm3) Type of rock found Top Bottom crust 30 2.2 - - 2.9 Silicic rocks. Andesite, basalt at base. Upper mantle 720 3.4 - - 4.4 Peridotite, eclogite, olivine, spinel, garnet, pyroxene. Perovskite, oxides. Lower mantle 2,171 4.4 - - 5.6 Magnesium and Silicon oxides. Outer core 2,259 9.9 - - 12.2 Iron+oxygen, suffur, Nickel alloy. Inner core 1,221 12.8 - - 13.1 Iron+oxygen, suffur, Nickel alloy. Total thickness 6,401
- 10. EVIDENCE THAT SATISFIES THE SEISMIC FINDING IN EARTH INTERIOR STUDY OF METEORITE A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon t About 86% of the meteorites are chondrites and are composed mostly of silicate minerals that appear to have been melted while they were free- floating objects in space Figure 5. falling meteorite (source: davidreneke,2016)
- 11. CONCLUSION Through seismological study of seismic wave emanating from an earthquake, much advances has been made in understanding the material makeup and composition of the earth interior. From conductive studies, the earth is divided majorly into the crust, the upper and lower mantle, the inner and outer core, with different composition, depth and thickness gain from the knowledge of seismic wave produced by earthquake.