importance of seismic wave to study of earth interior is indeed a useful material for advance studies

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.

12. THANKS FOR LISTENING